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The  Dental  College  Series  of  Text-Books. 


Dental  Chemistry  and 
Metallurgy. 


Fourth  Edition:  Revised,  Enlarged,  and  with 
Many  Illustrations 


BY 


CLIFFORD  MITCHELL,  A.M.,  M.D. 


FOURTH    EDITION. 


CHICAGO: 

The  W.  T.  Keener  Company, 

96  Washington  St., 

1896. 


^^    209     .  23^d  ST. 


C 


N.    t  .    V  ITY 


^ 


Copyright. 
Clifford  Mitchell,  A.  M.,  M.  D. 
1895. 


PRESS  OF 

W.  J    ANDERSON, 

CHICAGO. 


'i\(o  ^ 


TO  THE 

FOUI^XH    EDITION. 


^t*^ 


A  text-book  to  be  abreast  of  the  times  must  in  these 
days  be  conspicuous  for  its  quota  of  laboratory  work. 

The  present  edition  of  the  Dental  Chemistry  is  an 
effort  to  provide  the  student  with  a  course  which  shall 
include  a  large  number  of  exercises  in  experimental  chem- 
istry, both  inorganic  and  organic.  More  than  one  hund- 
red new  pages  have,  therefore,  been  inserted  in  the  book 
which  are  entirely  practical  in  character,  and  serve  to  illus- 
trate the  principles  covered  by  the  five  preceding  chapters. 
This  newwork  in  experimental  chemistry  has  been  followed 
by  an  outline  of  chemical  analysis,  the  reactions  of  the 
more  usual  metals  being  considered  at  much  greater 
length  than  in  previous  editions. 

Inasmuch  as  the  condition  of  the  teeth  has  to  do  with 
the  process  of  digestion,  experimental  work  in  this  edition 
includes  physiological  chemistry  in  which  that  of  digest- 
ion is  considered  at  some  length. 

Greater  attention  is  also  paid  in  this  edition  to  the 
germ  theory,  ptomaines,  leucomaines,  and  various  toxines, 
knowledge  of  which  has  grown  appreciably  since  the  first 
edition  of  this  book  was  issued.  Description  of  various 
new  alkaloids  and  antiseptics  will  also  be  found  in  the 
chapters  relating  to  them. 


IV  PREFACE. 

It  is  hoped  that  the  large  number  of  pages  now  relat- 
ing to  experiments  which  illustrate  the  general  principles 
of  chemistry  will  render  the  fourth  edition  more  accept- 
able to  those  instructors  who  insist  on  grounding  their 
students  thoroughly  in  pure  chemistry  before  attempting 
applied  science.  The  author  also  ventures  to  hope  that 
the  book  may  now  find  a  place  in  almost  any  college, 
whether  dental  or  medical,  where  the  principles  of  chem- 
istry are  taught.  All  the  matter  pertaining  to  dental 
chemistry  has,  however,  been  carefully  retained,  and  con- 
siderably more  added  with  reference  solely  to  the  needs  of 
the  dental  student  and  practitioner. 

In  conclusion  the  author  must  again  thank  the  dental 
profession  for  the  cordial  appreciation  of  his  humble 
-efforts.  The  demand  for  a  fourth  edition  in  the  course 
of  five  years  is  gratifying  to  any  one  interested  in  the 
application  of  chemistry  to  the  arts  and  sciences. 

In  connection  with  the  publication  of  the  fourth  edi- 
tion the  author  must  acknowledge  obligations  to  Messrs 
E.  H.  Sargent  &  Co.  for  numerous  cuts,  and  to  Dr.  W.  M. 
Thomas  for  aid  in  revising  the  proof.  The  author  must 
also  thank  his  publishers  for  materially  increasing  the 
size  of  the  book  without  adding  appreciably  to  its  selling 
price. 

70  State  st.,  January,  1896. 


TABLE  OF  CONTENTS. 


MGRA-^y 


•^: 


Chapter  I. — Physics: — Law,  theory,  phenomena,  mass, 
molecule,  atom,  molecular  motion,  atomic  motion, 
properties  of  matter  chemical  and  physical,  impene- 
trability, magnitude,  divisibility,  porosity,  compres- 
sibility, expansibility,  elasticity,  mobility,  cohesion, 
adhesion,  hardness,  brittleness,  tenacity,  malleabil- 
ity, ductility.  States  of  matter — solid,  liquid,  gas- 
eous, radiant;  machines,  levers,  planes,  wedge,  screw, 
friction,  capillarity,  specific  gravity,  density,  heat, 
distillation,  solution,  solubility,  crystallization,  cry- 
stals, light,  electricity,  electrolysis,  electricity  in  the 
mouth,  weights  and  measures,  metric  system,  per- 
centage solutions,  conversion  of  volume  to  weight, 
thermometry Pages  i  to  34 

Chapter  II. — Chemical  Philosophy:  — Molecule,  atom, 
element,  compound,  symbol,  table  of  constants  of 
the  elements,  writing  symbols,  atomic  weight,  posi- 
tive and  negative  elements,  quantivalence,  artiads 
andperissads,  compound  molecules,  law  of  definite 
and  multiple  proportions,  binary  compounds,  radi- 
cals, ternary  compounds,  acids,  bases,  salts,  how  to 
read  formulae,  ammonium  compounds,  nomenclature, 
— old  and  new,  chemical  change,  reactions,  laws  of 
double  decomposition,  insoluble  substances,  volatile 
compounds,  chemical  equations,  chemical  arith- 
metic, circumsta?ices  itifiue?ici?ig  chemical  attractio?i: 
Mendeleef's  tables  of  the  elements,  Lothar  Meyer's 
classification,  general  properties  of  the  metallic  ele- 
ments, general  properties  of  alloys  of  metallic  ele- 
ments   Pages  34  to  94 

Chapter  III. — Inorganic  Chemistry.  Monads: — Potas- 
sium, sodium,  [ammonium],  lithium,  silver,  hydro, 
gen,  iodine,  bromine,  chlorine,  fluorine,  and  theij. 
compounds. 


VI  TABLE    OF    CONTENTS. 

Dyads: — Barium,  calcium,  magnesium,  zinc,  cad- 
mium, lead,  uranium,  copper,  mercury,  tellurium,  sul- 
phur, oxygen,  and  their  compounds.  Amalgams: 
Rollin's  copper  amalgam,  Chandler's,  Weagent's 
processes,  Bogue's  process,  Ames's  process;  dejital 
amalgam,  alloys.  Compounds  of  mercury;  corrosive 
sublimate,  calomel,  vermilion;  compotmds  of  sulphur: 
action  of  sulphuretted  hydrogen  on  metals. 

Triads: — Bismuth,  gold,  antimony,  boron,  arsen- 
icum,  phosphorus,  nitrogen,  and  their  compounds. 
Gold:  occurrence,  preparation,  properties.  Re- 
fined gold,  chemically  pure  gold,  agents  used  for 
precipitating  gold,  crystal  gold,  beating  gold,  co- 
hesive gold,  corrugated  gold,  effect  on  gold  of  alloy- 
ing, appearance  of  gold  alloys,  gold  base  plate, 
compounds  of  gold,  purple  of  Cassius.  Phosphoric 
acid,  common  and  glacial.  Nitrogen  monoxide  or 
laughing  gas,  nitric  acid. 

Tetrads: — Aluminium,  cerium,  tin,  palladium, //^^/- 
inum,  iridium,  silicon,  titanium,  carbon,  and  their 
compounds.  Alums,  artificial  teeth,  enamels,  plat- 
inum, colors  for  enamels,  silex,  rutile. 

Hexads: — Manganese,  iron,  nickel,  cobalt,  chrom- 
ium, and  their  compounds.     Cobalt  blues.     Chromic 

oxide,  anhydride,  or  "acid" Pages  94  to  216 

Chapter  IV. — Organic  Chemistry.  Theory: — radicals, 
chains,  homologous  series,  types,  substitution,  de- 
rivatives, isomerism,  decomposition,  combustion  and 
decay,  fermentation,  putrefaction. 
Synopsis  of  Organic  Chemistry*. — ^Constitution 
and  derivation  of  300  organic  compounds. 

Class  I.  Hydrocarbons:— paraffins,  olefines,  acety- 
lenes. 

Class  II.  Monohydric  alcohols. 

Class  III.  Ethers. 

Class  IV.  Aldehydes. 

Class  V.  Ketones. 

Class  VI.  Fatty  acids  and  derivatives;  fats,  soaps, 

butter. 


*A  special  feature  of  the  fourth  edition,  enabling  the  student  by  reference  to  the 
index  to  classify  in  a  rational  manner  300  of  the  most  important  organic  compounds. 


TABLE    OF    CONTENTS.  Vll 

Class  VII.  Esters   or  ethereal  salts;  mercaptans, 

sulphides. 

Class  VIII.  Alkyl  compounds  of  nitrogen,  phos- 
phorus, arsenic,  antimony. 

Class  IX.  Glycols  or  diatomic  alcohols. 

Class  X.  Glycerins  or  triatomic  alcohols. 

Class  XI.  Carbohydrates. 

Class  XII.  Cyanogen  compounds  and  related  sub- 
stances.    Substances  related  to  uric  acid. 

Class  XIII.  Furfurane,  thiophene,  pyrrol. 

Class  XIV.  Aromatics  of  one  nucleus:  benzene 
series  and  derivatives.  Azo  and  diazo  compounds; 
hydrazines;  phenols;  quinones;  aromatic  alcohols; 
aromatic  acids  as  benzoic,  salicylic. 

Class  XV.  Aromatics  of  more  than  one  nucleus: 
phthaleins,  indigo,  naphthalenes,  naphthols,  pyridine, 
collidines,  etc. 

Class  XVI.  Alkaloids. 

Class  XVII.  Ptomaines, leucomaines,  toxalbumins. 

Class  XVIII.  Proteids. 

Class  XIX.  Ferments. 
Preparation  and  Properties  of  Important  Or- 
ganic Compounds: — Hydrocarbons:  paraffines,  min- 
eral oil,  vaseline,  oil  of  turpentine,  terpenes, 
essential  oils;  oil  of  cloves,  eugenol;  India-rubber, 
dental  rubber,  gutta-percha,  camphor,  resins,  myrrh, 
gums,  naphthalene,  naphthols.  Ethyl  series  of 
radicals,  alcohols,  alcohol.  Glycerine,  glycerites, 
boroglyceride,  glyceroborates.  Creosote.  Carbolic 
acid.  Phenol  compounds,  resorcin,  eucalyptol. 
Carbohydrates;  sugars,  honey,  gums,  collodion, 
celluloid.  Ethers:  chloroform,  iodoform,  iodol;  al- 
dehydes: paraldehyde,  chloral  hydrate.  Ketones. 
Organic  acids:  acetic,  trichloracetic,benzoic,  eugenic, 
hydrocyanic,  oleic,  oxalic,  lactic,  salicylic,  [salol, 
betol]  sozolic,  tartaric,  [tartar  emetic].  Alkaloids: 
aconitine,  atropine,  chinoline,  cannabine,  cocaine, 
morphine,  quinine,  strychnine,  veratrine,  "anti- 
pyrine",  "antifebrine,"  alstonine,  apomorphine, 
caffeine,  cytisine,  ditaine,  erythrophleine,  ethyl  oxy- 
caffeine,  hyoscyamine,  isatropyl  cocaine,  jerubebine, 
lamine,  oxy-propylene-di-iso-amylamine,  ulexine. 


viii  TABLE    OF    CONTENTS. 

List  of  Newer  Alkaloids  and  Glucosides,  with 
Derivation*: — Proteids:  albumins,  globulin,  etc. 
Fermentation.  Ferments.  Putrefactive  fermenta- 
tion in  the  mouth.  Fungi.  Bacteria.  Microbe  of 
dental  caries.  Pus  and  suppuration.  Disinfection: 
antiseptics,  germicides, disinfectants.  Miller  s  ?nouth 
washes.  Deodorizers.  Antiseptics:  alantol,  betol, 
bismuth  oxyiodide,  creolin,  cresylic  acid,  iodine 
trichloride,  mercuric  albuminate,  mercuric  oxy-cya- 
nide  oxy-naphthoic  acid,  tribrom-phenol,  sodium 
silico-.fluoride. 

Two  Hundred  New  Antiseptics  and  Therapeutic 
Agents: — *Antiseptics,  antituberculars,  hypnotics, 
analgesics,  antipyretics,  local  anaesthetics,  diuretics, 
uric  solvents,  mouth  washes.    Pages  216  to  339. 

Chapter  V. — The  Teeth  and  the  Saliva: — Tooth  struct- 
ure, chemical  constitution  of  the  teeth.  Enamel, 
dentine,  cement.  Table  of  analyses.  Action  of 
various  substances  on  the  teeth.  Chemistry  of 
caries;  chemical  theory,  vital  theory,  germ  theory. 
The  saliva:  physical  characters,  chemical  composi- 
tion, functions,  changes;  parotid  saliva,  submaxil- 
lary, sublingual;  buccal  mucus.  Tartar.  Salivary 
calculi Pages  339  to  360. 

Chapter  VI. — Laboratory  Course  Begun.  Experi- 
ments Illustrating  General  Principles  ofChem- 
iSTRvf: — Apparatus  and  manipulations.  Solution. 
Solutions  of  reagents,  insoluble  substances,  distilla- 
tion, sublimation,  precipitation,  chemical  change, 
physical  solution  and  chemical  solution,  chemical 
combination,  decomposition  of  compounds.  Nas- 
cent state.  Properties  of  acids  and  of  bases. 
Pages  360  to  397. 

Chapter  VII. — Laboratory  Work  Continued.  Practi- 
cal Chemistry  of  the  Elements  and  Their  Inor- 
ganic Compounds];: — Oxygen,  oxidation  and  reduc- 
tion, equations  illustrating  oxidation,  oxides,  anhy- 


*SpecJal  features  of  the  4th  edition. 
tSpecial  feature  of  the  4th  edition. 
^Special  feature  of  the  4th  edition. 


TABLE    OF    CONTENTS.  IX 

drides,  equations  illustrating  reduction,  hydric 
dioxide,  ozone,  hydrogen,  water,  nitrogen,  the  air; 
nitrogen  compounds,  ammonia,  laughing  gas,  nitro- 
gen dioxide,  nitric  acid,  carbon,  carbon  monoxide, 
carbon  dioxide,  sulphur,  sulphurous  oxide,  sul- 
phuric acid,  hydric  sulphide,  carbon  disulphide, 
phosphorus,  phosphoric  acid,  chlorine,  hydrochloric 
acid,  bromine,  iodine,  hydrofluoric  acid.  The  metals: 
sodium  and  compounds,  potassium  and  compounds, 
ammonium  compounds,  magnesium,  calcium,  alum- 
inum, iron,  manganese,  chromium,  zinc,  lead,  copper, 
bismuth,  silver,  mercury,  arsenic,  antimony,  gold 
and  their  compounds Pages  397  to  443 

Chapter  VIII. — Laboratory  Work  Continued.  Chem- 
ical Analysis.  The  Blowpipe: — Analysis  by  the 
blowpipe.  Flames,  oxidizing  and  reducing,  blowpipe 
materials,  the  Bunsen  flame,  short  method  of  blow- 
pipe analysis Pages  443  to  451. 

Chapter  IX. — Laboratory  Work  Continued.  Chemi- 
cal Analysis.  Reactions  of  The  Metals"'^: — Re- 
actions of  compounds  of  the  following  elements: 
silver,  lead,  mercury,  (— ous),  mercury  ( — ic),  cop- 
per, bismuth,  arsenicum  ( — ous),  arsenicum  ( — ic); 
special  tests  for  both  arsenous  and  arsenic  com- 
pounds: heat  tests,  Reinsch's  test,  the  Marsh  test, 
Fleitmann's  test,  Bettendorf's  test.  Antimony,  tin 
( — ous),  tin  ( — ic),  gold,  platinum,  iron  ( — ous  and 
— ic),  manganese,  chromium,  zinc,  aluminium,  nickel, 
cobalt,  barium,  calcium,  strontium,  magnesium,  am- 
monium, sodium,  and  potassium.. .  Pages  451  to  477. 

Chapter  X. — Laboratory  Work  Continued.  Chemical 
Analysis.  Qualitative  Analysis: — Short  scheme 
for  qualitative  analysis  of  the  metals  of  Chapter  IX. 
Analysis  of  an  aqueous  or  slightly  acid  solution  of 
ordinary  compounds  of  the  metals.*  The  five  groups 
of  metals.     Separations.* Pages  477  to  486. 

Chapter  XI. ^Laboratory  Work  Continued.  Chemi- 
cal Analysis.     Reactions  of  Aciosf: — Acidulous 

♦Special  feature  of  the  4tfi  edition. 
tSpecial  feature  of  the  4th  edition. 


X  TABLE    OF    CONTENTS. 

radicals:  reactions  of  carbonates,  sulphides,  chlo- 
rides, bromides,  iodides,  cyanides,  nitrates,  chlo- 
rates, chromates,  sulphites,  sulphates,  phosphates, 
borates,  acetates,  oxalates,  tartrates.  Short  scheme 
for  identification  of  the  acidulous  radicals. 
Pages  486  to  495. 

Chapter  XII. — Laboratory  Work  Continued.  Chemi- 
cal Analysis.  Organic  Analysis:* — Reactions  of 
phenol,  chloroform,  alcohol,  glycerin,  ether,  the 
alkaloids,  deportment  of  alkaloids  with  general  re- 
agents   Pages  495  to  502. 

Chapter  XIII. — Laboratory  Work  Continued.  Chemi- 
cal Work  in  the  Dental  Laboratory: — Refining 
gold,  testing  amalgams,  manipulating  vulcanite, 
compounding  rubber.  Short  method  of  qualitative 
and  quantitative  analysis  of  dental  amalgam  alloys. 
Analysis  of  cements.  Testing  rubbeis. 
Pages  502  to  517. 

Chapter  XIV. — Laboratory  Work  Continued.  Ex- 
periments IN  Physiological  CnEMiSTRYf: — Prop- 
erties of  starch,  action  of  acids  on  starch,  action  of 
heat,  ferments,  saliva,  and  pancreatic  fluid  on  starch. 
Reactions  of  the  sugars:  Haines's  test,  Fehling's 
•  test,  Trommer's  test.  Fermentation  of  sugars. 
Glycogen.  Fats  and  oils.  Saponification.  Gly- 
cerin. Fatty  acids.  Emulsions.  Crystallization 
of  fats.  General  characters  of  the  proteids.  Tests 
of  proteids:  Xantho-proteic  reaction,  Millon's  test, 
biuret  test.  ■  Separation  of  peptones.  Character- 
istics of  individual  proteids.  Digestion  of  proteids: 
gastric  digestion,  pancreatic  digestion.  The  gastric 
juice:  free  acid,  determination  of  total  acidity,  of 
free  HCl,  of  organic  acids,  Boas's  test  for  cancer. 
The  blood:  properties,  tests,  chemical  and  micro- 
scopical  Pages  5 1 7  to  547. 

Chapter  XV. — Laboratory  Work  Concluded: — Chemi- 
cal analysis  of  saliva,  teeth,  tartar,  and  urine.   Com- 


♦Special  feature  of  the  4th  edition. 
fSpeciaf  feature  of  tfie  4th  edition. 


TABLE    OF    CONTENTS.  XI 

plete  course  in  salivary  analysis.  Qualitative  tests 
for  normal  constituents  of  the  saliva.  Quantitative 
analysis,  volumetric  and  gravimetric.  Special  tests 
for  constituents  of  oral  secretions.  Detection  of 
mercury  in  saliva.  Microscropic  examination  of 
the  salivary  sediment.  Morphology  of  the  human 
sputum.  Analysis  of  teeth,  qualitative  and  quanti- 
tative.    Short  course  in  urinary  analysis. 

Pages  547  to  564 

Index* Pages  564  to  586 

*A  special  feature  of  the  4th  edition  is  the  new  index  of  1,850  terms  as  compared 
with  1,000  terms  in  the  3d  edition. 


Dental  Chemistry  and  Metallurgy 


CHAPTER  I. 
Physics. 

1.  Introduction: — 

Matter  is  the  term  given  to  that  which  occu- 
pies space  and  possesses  weight.  Matter  in  other 
words  is  the  object  of  sense,  our  knowledge  of 
the  material  world  being  founded  upon  experi- 
ence or  the  evidence  of  our  senses.  A  body  is  a 
definite  and  limited  portion  of  matter,  as,  for  exam- 
ple, a  dust  particle,  a  stone,  an  aerolite,  or  a  planet. 
The  different  kinds  of  matter  as  water,  lime,  sil- 
ver, coal  are  known  as  substances.  Every  object, 
body,  or  substance  which  can  be  perceived  by  at 
least  one  of  the  senses  is  composed  of  matter: 
thus,  though  air  can  not  be  seen,  it  can  be  felt 
when  in  motion,  as  wind,  therefore  air  is  matter. 


2  DENTAL    CHEMISTRY, 

The  characteristics  of  the  objects  about  us  are  differ- 
ent: some  are  liquid,  some  solid,  some  large,  some  small: 
moreover  they  are  concerned  in  certain  events  or  occur- 
rences which  naturally  take  place;  for  example  we  see 
that  rain  falls,  a  balloon  rises,  a  ship  floats,  a  piece  of 
lead  sinks.  These  events  are  what  are  known  as  phe?iom- 
ena  or  things  which  occur.  Phenomena  are  innumerable. 
The  study  of  science  is  the  study  of  the  relations  between 
objects  and  between  phenomena.  A  scientific  law  is  a 
generalized  statement  of  what  has  been  observed  to  oc- 
cur. A  law  is  not  a  cause.  A  law  is  not  always  a  theory. 
A  theory  is  the  most  perfect  expression  of  physical  truth 
and  is  deduced  from  both  laws  and  principles  that  have 
been  established  on  independent  testimony.  The  terms 
law,  theory,  and  hypothesis  are,  however,  often  used  inter- 
changeably. An  hypothesis  is  a  guess  or  assumption 
which  when  more  completely  developed  and  probable 
becomes  a  theory,  which  in  turn  accounts  for  a  law. 
Again  what  has  been  merely  an  hypothesis  may  subse- 
quently become  a  theory,  and  a  theory  may  in  time  be- 
come so  well  confirmed  as  to  be  regarded  as  a  highly 
probable  law.  Theories  are  indispensable,  for  they  aid  in 
directing  investigation,  and  thus  lead  to  truth.  The 
atomic  theory  or  hypothesis  alone  enables  us  to  account 
for  most  of  the  phenomena  of  matter.  It  was  proposed 
by  John  Dalton  in  1807  and  presupposes  the  existence  of 
atoms. 

2.  Atoms:— 

An  atom  is  the  smallest  division  of  elementary 
matter  recognized  as  existing  and  which  can  by 
combining  form  the  molecule.  There  are  only 
about  70  different  kinds  of  atoms,  whose  com- 
binations form  the  universe. 


PHYSICS.  6 

3.  Molecules:— 

A  molecule  is  the  smallest  part  of  any  sub- 
stance which  can  exist  alone  and  exhibit  the  prop- 
erties of  that  substance.  A  molecule  is  a  cluster 
of  two  or  more  atoms  bound  together  by  what 
we  call  chemical  affmity.  Neither  molecules  nor 
atoms  can  be  seen  by  the  microscope. 

Molecules  may  be  composed  of  any  number  of  atoms 
and  while  there  are  only  about  70  kinds  of  atoms  there  is 
practically  no  limit  to  the  different  kinds  of  molecules. 
Molecules  differ  in  kind,  number,  and  arrangement  of  the 
atoms  which  compose  them.  Each  molecule  in  a  body 
is  separated  from  its  neighbor  by  inconceivably  small 
space,  and  has  a  quivering  motion,  rebounding  from  its 
neighbors.  Heat  increases  the  size  of  a  body  because 
each  molecule  then  moves  faster  and  pushes  its  neighbor 
farther  away. 

4.  Mass: — The  term  mass  is  given  to  a  quan- 
tity of  matter  made  up  of  molecules  and  appreci- 
able to  the  senses. 

5.  Divisions  of  matter: — Mass,  molecule, 
atom. 

6.  Attraction  of  Mass,  or  molar  attraction:  same  as 
attraction  of  gravitation  or  tendency  of  bodies  to  ap- 
proach one  another. 

7.  Molecular  Attraction. — Cohesion  or  adhesion. 

8.  Atomic  Attraction. — Chemism  or  chemical  affinity. 

9.  Molar  Motion. — The  ordinary,  visible,  mechanical 
motion,  as  that  of  a  machine  or  its  parts. 


DENTAL    CHEMISTRY. 


10.  Molecular  Motion. — Heat,  light,  magnetism,  elec- 
tricity. 

11.  Atomic  Motion. — A  constant  revolution  or  swing- 
ing of  the  atom  within  a  limited  space. 

12.  Properties  of  Matter. — Qualities  char- 
acteristic of  matter.  Two  kinds,  chemical  and 
physical. 

13.  Chemical  Properties. — Those  resulting- 
from  the  composition  of  the  molecule  with 
reference  to  its  atoms  and  shown  only  by 
change  of  identity  of  the  molecule:  as  com- 
bustibility, explosibility,  etc. 

14.  Physical  Properties  of  Matter.— The 
different  ways  in  which  matter  presents  itself 
to  our  senses.  Two  kinds,  g;eneral  and  specific, 
or  universal  and  characteristic.  General 
properties  are  those  common  to  all  matter,  as 
impenetrability,  extension,  porosity,  etc. 
Si)ecific  properties  are  those  observed  in  cer- 
tain bodies  only,  or  in  certain  states  of  those 
bodies,  as  solidity,  color,  tenacity,  etc.  Physi- 
cal properties  may  be  shown  without  change  in 
the  identity  of  the  molecule. 

15.  Pliysical  Properties:  Impenetrability. — Prop- 
erty of  matter  in  virtue  of  which  two  bodies  cannot 
occupy  the  same  space  at  the  same  time.  Example: 
nail  driven  into  wood,  particles  of  wood  make  way  for 
the  nail. 

16.  Extension  or  Magnitude. —  Property  in  virtue  of 
which  every  body  occupies  a  limited  portion  of  space. 

17.  Divisibility.— Property  of  matter  by  virtue  of 
which  a  body  may  be  separated  into   distinct   parts.     Di- 


PHYSICS.  5 

* 

visibility  of  matter  practically  limited  before  molecule  is 
reached;  theoretically  should  be  limited  by  the  atom. 

1 8.  Porosity. — Quality  in  virtue  of  which  spaces  or 
pores  exist  between  the  molecules  of  a  body.  Example: 
lead,  if  hammered,  is  made  smaller  because  the  size  of 
the  pores  is  reduced,  the  molecules  being  forced  nearer 
together. 

19.  Compressibility. — Property  in  virtue  of  which  a 
body  may  be  reduced  in  size;  it  is  a  consequence  and 
proof  of  porosity. 

20.  Expansibility. — Property  in  virtue  of  which  a 
body  may  be  increased  in  size.  Opposite  of  compressi- 
bility. Example:  iron  when  heated  becomes  larger  or 
expands  because  its  molecules  are  pushed  further  apart. 

21.  Elasticity. — Property  in  virtue  of  which  bodies 
resume  their  original  form  or  volume  (size)  when  that 
form  or  volume  has  been  changed  by  external  force. 
Example:  apiece  of  Ordinary  rubber  after  being  stretched 
out  resumes  its  original  size  when  the  force  stretching  it 
ceases  to  act. 

22.  Mobility. — Property  in  virtue  of  which  the  posi- 
tion of  a  body  may  be  changed.  Inertia  is  the  incapa- 
bility of  matter  to  change  its  own  state  of  motion  or  rest. 
Example:  a  book  on  a  table  cannot  move  itself  and  is 
said  to  have  inertia;  it  can  move,  however,  when  sufficient 
force  is  applied  to  it  and  is  said  to  have  mobility. 

23.  Cohesion. — Force  which  unites  mole- 
cules of  the  same  kind  as  two  molecules  of 
water  or  two  molecules  of  iron.  Cohesion 
holds  substances  tog^ether  and  gives  them 
form. 

24.  Adhesion. — Force  which  unites  mole- 
cules of  different  kinds.  Example:  dip  a  glass 
rod  into  water  and,  on  withdrawing  it,  a  drop 


Q  DENTAL   CHEMISTRY. 

4 

will  be  found  at  its  lower  extremity,  which  re- 
mains suspended  or  adheres  to  it. 

25.  Hardness. — Property  in  virtue  of  which 
some  bodies  resist  attempts  to  force  passage 
between  their  particles.  Example:  a  tooth 
possesses  hardness. 

26.  Brittleness.  —  Property  in  virtue  of 
which  some  bodies  may  easily  be  broken.  Ex- 
ample: glass  is  not  only  hard,  but  is  also  easily 
broken  or  brittle. 

2^.  Tenacity. — Property  in  virtue  of  which 
some  bodies  resist  attempts  to  pull  their  par- 
ticles asunder.  Example:  an  iron  wire  is  diffi- 
cult to  pull  apart  and  is  said  to  be  tenacious. 

Tenacity  is  proportional  to  sectional  area:  a 
rod  of  one  square  inch  sectional  area*  will 
carry  twice  the  load  that  a  rod  of  the  same 
material  with  sectional  area  of  half  a  square 
inch  will  carry. 

28.  Malleability.  —  Property  in  virtue  of 
which  some  bodies  may  be  hammered  or  roll- 
ed into  sheets.  Example:  gold  can  be  beaten 
into  sheets  so  thin  that  nearly  300,000  are 
necessary  to  measure  an  inch  in  height  when 
they  are  placed  one  on  another. 

29.  Ductility.— Property  in  virtue  of  which 
some  bodies  may  be  drawn  into  wire.  Ex- 
ample: iron  when  heated  may  be  drawn  into 
a  wire,  hence  is  said  to  be  ductile. 


♦The  sectional  area  of  a  substance  as,  for  example,  a  rod,  is 
that  of  the  surface  of  its  cross  section. 


30.  States  of  Matter.  —  Solid,  liquid,  g-as- 
ous,  and  radiant.  In  the  first,  the  attraction  of 
the  molecules  is  greater  than  their  repulsion. 
In  the  second,  their  attraction  and  repulsion 
are  equal.  In  the  third,  repulsion  is  greater 
than  attraction.  In  the  fourth,  so  few  mole- 
cules are  in  the  given  space  that  they  rarely 
strike  each  other  in  their  paths  of  motion. 

Fluid  is  a  term  applied  to  any  thingf 
which  will  adapt  itself  to  the  sides  of  the  ves- 
sel containing:  it,  hence  includes  both  liquids 
and  gases. 

Yapors  are  g:ases  produced  by  heat 
from  substances  usually  solid  or  liquid  at  or- 
dinary temperatures. 

Examples:  solids:  wood,  metals ;yf^/</5.- 
air,  water;  liquids:  water,  oil,  alcohol;  gases: 
air,  oxygen,  hydrogen;  vapor:  steam. 

31.  Force. — Cause  tending  to  produce,  change,  or  de- 
stroy motion.  Example:  gravity,  friction,  electrical  or 
magnetic  attraction,  etc. 

32.  Work. — Overcoming  of  resistance. 

33.  Energy. — Power  of  doing  work. 

34.  Foot-pound. — Amount  of  work  required  to  raise 
one  pound  one  foot  high.* 

35.  Horse-power. — Ability  to  perform  33^000  foot- 
pounds in  a  minute. 

36.  Machine. — Contrivance   for    utilizing    energy   by 

*The  work  required  to  raise  one  kilogram  through  one  meter, 
against  the  force  of  gravity,  is  called  a  kilogram-meter. 


DENTAL   CHEMISTRY. 


which  power  can  be  applied  more  advantageously  to  resist- 
ance and,  in  general,  intensity  of  energy  be  transformed. 

37.  Laws  of  Machines. — i.  Gain  in  intensity  of  power 
=loss  in  time,  velocity,  or  distance  and  vice  versa. 

2.  Power  X  distance=weight  X  distance. 

3.  Power  X  velocity^weight  X  velocity. 

38.  Lever. — Any  inflexible  bar,  straight  or  curved, 
resting  on  a  fixed  point  or  edge  called  iae.  fulcrwH.  Every 
lever  has  two  arms,  the  power-arm  and  the  weight-arm. 
The  power-arm  is  the  perpendicular  distance  from  the 
fulcrum  to  the  line  in  which  the  power  acts;  the  weight- 
arm  is  the  perpendicular  distance  from  the  fulcrum  to  the 
line  in  which  the  weight  acts. 

When  the  lever  is  not  a  straight  bar,  or  when 
power  and  weight  do  not  act  parallel  to  each  other,  the 
lever  is  called  a  bent  lever. 

39.  Kinds  of  Levers. — ( i  )Fulcrum  between  power  and 
resistance  (weight)  as  in  crowbar,  (2)weight  between 
power  and  fulcrum  as  in  wheelbarrow,  (3)  power  between 
weight  and  fulcrum  as  in  human  forearm. 

40.  Laws  of  the  Lever.— 

Power  X  power-arm^weight  X  weight-arm. 

A  given  power  will  support  a  weight  as  many  times  as 
great  as  itself,  as  the  power-arm  is  times  as  long  as  the 
weight-arm. 

The  continued  product  of  the  power  and  lengths  of  the 
alternate  arms  beginning  with  the  power-arm^the  con- 
tinued product  of  the  weight  and  lengths  of  the  alter- 
nate arms  beginning  with  the  weight-arm. 

41.  Law  of  Wlieel  and  Axle. — The  power  multiplied 
by  the  radius,  diameter,  or  circumference  of  the  wheel= 
the  weight  X  the  corresponding  dimension  of  the  axle. 

42.  Pulley. — A  wheel,  turning  on  an  axis,  provided 
with  a  cord,which  passes  over  the  grooved  circumference  of 
thewheel.    The  axis  is  supported  by  a  frame  called  thcblock. 


PHYSICS.  9 

43.  Inclined  Plane. — Hard,  smooth,  inflexible  surface 
used  in  most  cases  to  aid  in  the  performance  of  work 
against  the  force  of  gravity.  It  is  inclined  so  as  to  make 
an  oblique  angle  with  the  direction  of  the  force  to  be 
overcome,  and  in  most  cases  is  inclined  to  the  horizon  at 
an  acute  angle. 

44.  Wedge. — Movable  inclined  plane  in  which  power 
usually  acts  in  a  direction  parallel  to  base.  It  is  used  for 
moving  great  weights  short  distances.  More  commonly 
a  wedge  is  two  inclined  planes  united  at  their  base.  With 
given  thickness,  the  longer  the  wedge  the  greater  the 
gain  in  intensity  of  power. 

45.  Screw. — Cylinder  with  spiral  groove  or  ridge,  called 
the  thread,  winding  about  its  circumference.  By  aid 
of  the  screw  a  given  power  will  support  a  weight  as  many 
times  greater  than  itself  as  the  circumference  described 
by  the  power  is  times  as  great  as  the  distance  between 
two  adjoining  turns  of  the  thread. 

46.  Friction. — Resistance  encountered  by  a  moving 
body  from  the  surface  on  which  it  moves.  Is  greatest  at 
beginning  of  motion,  increases  with  roughness  of  sur- 
faces, greater  between  soft  bodies  than  hard  ones,  is 
nearly  proportional  to  pressure,  is  not  affected  by  extent 
of  surface  within  ordinary  limits,  is  greater  between  sur- 
faces of  the  same  material  than  between  those  of  differ- 
ent kinds;  rolling  friction  less  than  sliding  friction; 
friction  diminished  by  polishing  or  lubricating  the 
surfaces. 

47.  Capillarity. — When  a  glass  rod  is  placed  verti- 
cally in  water  the  latter  rises  above  its  level  at  the  sides 
of  the  glass.  The  finer  the  rod  the  greater  the  capillary 
ascent.  If  the  rod  be  dipped  into  a  liquid  which  does  not 
wet  it,  as  mercury,  the  liquid  will  be  depressed  instead  of 
raised. 

48.  Displacement. — A  body  which  sinks  in  water  dis- 


IQ  DENTAL   CHEMISTRY. 

places  exactly  its  own  bulk  of  water  and  loses  in  weight 
an  amount  just  equal  to  the  weight  of  water  displaced. 

49.  Specific  Gravity.— Relative  weig-hts  of 
equal  bulks  of  bodies  referred  to  an  assumed 
standard;  for  liquids  and  solids,  the  standard  is 
distilled  water  at  a  temperature  of  4°  C.  or 
39.2°  F.  For  gases,  the  standard  is  air  or  hy- 
drog-en.  If  a  substance  weighs  four  times  as 
much  as  the  same  bulk  of  water,  it  is  said  to 
have  a  sp.  gr.  of  4. 

50.  Calculation  of  Specific  Gravity  of 
Solids  and  Liquids.— (<^)  For  solids  use  the  fol- 
lowing formula: 

W 
Sp.  gr.= 

w— W^ 

in  which  W=  weight  of  body  in  air,  W^  its 
weight  in  water  (suspended  by  a  light  thread 
from  the  scale  pan).  Example:  weight  of  a 
body  in  air,  i.  e.,  ordinary  weight,  is  50  ounces; 
its  weight  in  water  is  42  ounces.        W=5o, 

W      50 

W^=42,  W— W^=5o— 42or8; =—=6.25, 

W— W    8 
sp.  gr.     In  other  words  the  weight  of  the  body 
divided  by  the  weight  of  an  equal  volume 
(bulk)  of  water  is  the  specific  gravity  of  the 
body. 

(<^)If  the  body  is  lighter  than  water,  fasten  a 
heavy  body  to  it  and  weigh  in  water.  Weigh 
the  heavy  body  in  water.    Weigh  the   light 


PHYSICS.  .  ]^2 

body  in  air.  Then  subtract  the  water  weight 
of  the  combined  mass  from  the  water  weight 
of  the  heavy  body,  and  add  to  the  difference 
the  air  weight  of  the  hght  body.  Then  divide 
air  weight  of  cork  by  the  sum.  Example:  re- 
quired to  find  the  specific  gravity  of  a  piece  of 
cork.    Attach  to  it  a  piece  of  iron: 

1.  Weight  of  combined  mass  in  water     -     51.5  grains. 

2.  Weight  of  iron  in  water         -         .         _     66.9  grains. 

3.  Weight  of  cork  in  air        -         -        -  4.6  grains. 

4.  66.9—51.5=15.4. 

5.  15.4+4.6=20. 

4.6 

6.   =0.23,  sp.  gr.  of  cork. 

20 

{c)  To  find  the  sp.  gr.  of  soHds  which  dis- 
solve in  water,  weigh  them  in  some  liquid  in 
which  they  are  insoluble,  and  find  the  specific 
gravity  as  before.  Multiply  result  by  specific 
gravity  of  liquid  used  and  the  product  will  be 
the  true  specific  gravity.  Example:  to  find 
specific  gravity  of  sugar.  Suppose  it  weighs 
10  grains  in  air  and  4.56  grains  in  oil  of  tur- 
pentine. 10 — 4.56=5.44  grains.  io-:-5.43=i.84 
or  sp.  gr.  referred  to  turpentine.  Ascertain  from 
tables  the  sp.  gr.  of  turpentine(==o.86),  multi- 
ply 1.84  by  0.86,  and  the  product,  1.58,  is  the 
true  sp.  gr.  of  the  sugar. 

(d)  To  find  the  specific  gravity  of  a  powder 
insoluble  in  water,  weigh  a  flask  empty;  weigh 
the  flask  full  of  water;  weigh  the  flask  partly 
full  of  the  powder;     fill  the   flask  now  con- 


12 


DENTAL   CHEMISTRY. 


tainingf  powder  full  of  water  and  weigh 
again.  Subtract  weight  of  flask  filled  with 
water  from  weight  of  flask  filled  with  powder 
and  water  mixed.  The  difference  will  be  the 
loss  of  weight  of  the  powder.  Divide  the  weight 
of  the  powder  in  air  by  the  loss  of  weight  in 
water,  and  the  quotient  will  be  the  specific 
gravity  of  the  powder. 

(^)  To  find  the  sp.  gr.  of  liquids  a  special 
flask,  called  a  picnometer  or  sp.  gr.  flask,  is 
used  which  contains  a  certain  weight  of  water 
when  filled.  This  weight  is  marked  on  the 
flask.  To  ascertain  the  sp.  gr.  of  a  liquid  by 
means  of  its  use,  weigh  it,  fill  it  with  the  liquid 
and  weigh  it,  subtract  weight  of  flask,  and 
divide  difference  by  number  marked  on  the 
flask.  The  quotient  will  be  the  sp.  gr.  of  the 
liquid.  The  temperature  of  the  liquid  should 
be  that  marked  on  the  flask. 

Instruments  called  hydrometers'^  are  also 
used  for  finding  the  sp.  gr.  of  liquids,  and  are 
long,  narrow,  glass  or  metal  tubes  provided 
with  a  bulb  near  the  bottom  filled  with  air,  and 
a  smaller  one  below  it  filled  with  mercury.  To 
find  the  sp.  gr.  it  is  merely  necessary  to  drop 
the  hydrometer  into  the  liquid  and  read  off  the 
number  on  the  scale  at  the  surface  of  the  liquid. 

♦Hydrometers  should  be  those  carefully  standardized  to  a  certain 
temperature,  as  77"  F.,  and  used  in  liquids  warmed  or  cooled  to  that 
temperature. 


PHYSICS. 


13 


51.  Density. — In  chemistry,  the  term  density 
should  mean  the  weight  of  a  gas  referred  to 
hydrogen  as  a  unit.  [Specific  gravity  of  gases 
means  their  weight  referred  to  air  as  a  unit. 
Thus  the  density  of  chlorine  is  said  to  be  35.5, 
but  its  specific  gravity  2.47.  This  means  that 
chlorine  is  35.5  times  as  heavy  as  hydrogen, 
but  2.47  times  as  heavy  as  air.  In  this  book 
the  term  density  will  be  used  only  in  the  case 
of  gases.  In  some  books  the  term  density  is 
used  to  mean  specific  gravity  and  is  applied 
to  solids]. 

52.  Law  of  Avogadro. — Equal  volumes  of  all  bodies 
in  the  state  of  gas,  and  at  the  same  temperature  and 
pressure,  contain  the  same  number  of  molecules.  Hence 
(«)  the  specific  gravities  of  any  twogasesare  to  each  other 
as  the  weights  of  their  molecules,  and  {b^  their  molecules 
are  all  of  the  same  size.* 

53.  Law  of  Mariotte. — Volume  of  a  confined  gas  is 
inversely  proportional  to  the  pressure.  That  is,  the 
greater  the  pressure  the  less  the  volume  and  vice  versa. 
The  standard  pressure  is  760  millimetres  or  30  inches  of 
the  barometric  pressure. 

54.  Law  of  Charles. — Volume  of  a  gas  varies  directly 
with  the  absolute  temperaturef.  That  is,  the  cooler  the 
gas  the  smaller  its  volume,  and  vice  versa.  A  gas  ex- 
pands 273  its   volume  in  passing   from  0''  to   1°  C.  or  iJo  its 


volume  for  one  degree  Fahrenheit. 


*Avogadro's  law  finds  application  in  the  determination  of  mole- 
cular weights. 

tThe  temperature  of  — 273"  C.  is  called  the  absolute  zero  of 
temperature.  Absolute  temperatures  are  obtained  by  adding  273  to 
the  reading  on  the  Centigrade  thermometer. 


14 


DENTAL   CHEMISTRY. 


55.  Standard  Temperature  and  Pressure. —  c°  C. 

and  760  m.  m.  pressure.     (See  page  32) 

56.  Effects  of  Heat. — In  general,  heat  in  the  first  place 
expands  bodies,  then  overcomes  cohesion  to  such  ex- 
tent that  the  body  melts  and  becomes  liquid,  then  finally 
overcomes  cohesion  entirely  and  the  liquid  boils  and 
passes  into  the  gaseous  state. 

57.  Laws  of  Fusion. — ( i )  Every  solid  begins  to  melt 
at  a  certain  temperature,  which  is  invariable  for  the  given 
substance  if  the  pressure  be  constant.  When  cooling, 
the  substance  will  solidify  at  the  temperature  of  fusion. 
(2).  The  temperature  of  the  solid,  or  liquid,  remains  at 
the  melting  point  from  the  moment  that  fusion  or  solidifi- 
cation begins  until  it  is  complete. 

58.  Thermal  Unit. — Amount  of  heat  necessary  to 
raise  one  pound  of  water  from  0°  C.  to  1°  C,  or  1390  foot 
pounds.  Sometimes  applied  to  amount  of  heat  necessary 
to  raise  one  pound  of  water  from  32°  to  33"  F.,  or  772  foot 
pounds. 

59.  Specific  Heat. — When  equal  weights  of  different 
bodies  are  raised  through  the  same  number  of  degrees  of 
temperature,  they  take  up  different  amounts  of  heat; 
that  is,  different  bodies  possess  different  capacities  for 
heat.  Thus  the  amount  of  heat  needed  to  raise  a  kilo- 
gram of  water  through  100°  C.  is  31  times  as  great  as  that 
needed  to  raise  the  same  weight  of  platinum  through  the 
same  interval  of  temperature.  Water  then  being  taken 
as  a  unit,  the  specific  heat  of  platinum  is  3\  or  0.032. 

60.  Boiling  Point.— Temperature  at  which  a  liquid 
gives  off  vapor  rapidly  from  the  whole  liquid;at  sea  level 
boiling  point  of  water  is  100°  C.  or  212°  F.  Superheated 
steam  is  the  result  of  applying  considerable  pressure 
to  a  boiling  liquid,  when  its  temperature  will  rise  until 
the  tension   of  the   steam   will    cvercbme   the   pressure. 


PHYSICS. 


15 


6i.  Evaporation. — Quiet  formation  of  vapor  at  the 
surface  of  a  liquid. 

62.  Distillation. — Conversion  of  a  liquid  into  gas  and 
recondensation  of  the  gas  into  liquid.  Operation  per- 
formed in  a  still,  consisting  of  a  retort  in  which  the  liquid 
is  boiled  and  a  condenser  for  changing  the  vapor  back  to 
liquid. 

63.  Fractional  Distillation.  —  Different  substances 
boil  at  different  temperatures.  Raising  the  temperature 
of  a  mixture  of  two  liquids  to  a  point  above  the  boiling 
point  of  one,  but  below  that  of  the  other,  will  vaporize 
the  one  but  not  the  other. 

64.  Destructive  Distillation.— Distillation  of  dry  sub- 
stances so  as  to  destroy  them  and  obtain  liquids  or  gases. 
Example:  coal  for  illuminating  gas. 

65.  Sublimation. — Such  solids  as  do  not  melt  when 
heated,  but  pass  directly  into  vapor,  are  said  to  sublime. 
Example:  camphor. 

66.  Solution. — May  be  either  ^physical  or 
chemical. 

Physical,  either  {a)  result  of  adhesion  of 
liquid  to  solid  overcoming-  cohesion  of  mole- 
cules of  the  solid,  or  {b)  feeble  combination  of 
the  solid  with  water  and  diffusion  of  this  com- 
pound through  remaining-  water.  Example  of 
{d)\  sugar  dissolved  in  water;  on  boiling  away 
the  water  the  sugar  may  be  recovered  entirely 
unchanged.  Example  of  (^):  dried  alum  when 
dissolved  in  water  separates  again  in  crystals 
in  which  water  is  found. 

Chemical  when,  by  chemical  action  between 
two  substances,  a  soluble  compound  is  formed, 
which  dissolves  in  the  water    present.     Ex- 


X6  DENTAL   CHEMISTRY. 

ample:  silver  forms  with  nitric  acid  by  chemi- 
cal action  a  soluble  compound,  silver  nitrate, 
which  then  dissolves  in  water  that  may  be 
present.  Similarly  an  acid,  attacking-  tooth 
structure,  forms  more  or  less  soluble  com- 
pounds with  the  lime  and  magnesia  of  the 
tooth. 

67.  Solvents. — All  liquids  are  solvents. 
Water  is  the  best  general  solvent  especially 

for  metallic  salts.  Alcohol  is  the  best  solvent 
for  resins.  Mercury  dissolves  many  metals. 
Gases  may  be  dissolved  in  liquids.  Some 
liquids  dissolve  in  liquids,  as  essential  oils  in  al- 
chohol,and  the  process  is  z2Xi^diliqiiid diffusion. 

68.  Saturated  Solution.— When  a  liquid 
has  dissolved  all  of  a  solid  that  it  can  at  a  given 
temperature,  the  solution  is  called  a  saturated 
one. 

69.  Solubility.— The  solubility  of  a  sub- 
stance is  denoted  by  the  amount  of  it,  by 
weight,  which  a  given  amount  of  a  solvent,  as 
water  or  alcohol,  will  take  up  at  a  given  tem- 
perature. Thus  one  part  of  alum  is  soluble  in 
10.5  parts  of  water  at  59"  F. 

70.  Deliquescence.- Bodies,  which  absorb 
water  from  the  air  and  become  liquid,  are  said 
to  deliquesce.  Example:  zinc  chloride.  Such 
substances  are  said  to  be  hygroscopic. 

71.  Efflorescence.  —  Substances,  which  on 
exposure  to  air  lose  water  from  their  crystals, 


PHYSIC.  17 

are  said  to  effloresce.     Example:  ferrous  sul- 
phate (ordinary  green  vitriol.) 

72.  Dialysis. —  Liquid  diffusion,  when  liquids  are 
separated  by  some  porous  diaphragm  as  bladder  or  parch- 
ment paper.  Passage  of  liquid  through  the  diaphragm  is 
called  Osmosis. 

73.  Dialyzer. — Glass  cylinder  open  at  one  end  and 
closed  at  the  other  by  the  membrane  used  as  a  separating 
medium. 

74.  Colloids  and  Crystalloids. — Easily  crystallizable 
bodies  pass  through  the  membranes  readily.  Those 
which  do  not  crystallize  pass  through  with  difficulty  and 
are  called  colloids.  Examples:  crystalloid,  alum;  colloid, 
gelatine. 

75.  Dialysate. — Term  applied  to  a  substance  which 
has  been  dialyzed,  i.  e.  has  passed  through  the  membrane 
of  the  dialyzer. 

76.  Crystals. — Solid  substances  bounded  by 
plane  surfaces  symmetrically  arranged  accord- 
ing" to  fixed  laws.     (See  Section  80). 

77.  Crystallization. — Change  of  substances 
from  melted  state  or  solution  to  solid  state, 
with  assumption  of  geometrical  form.  Essen- 
tial condition,  possibility  of  free  motion  of 
smallest  particles. 

78.  Amorphous— Polymorphous. — A  body 
never  obtained  in  crystalHne  state  is  said  to  be 
amorphous,  i.  e.,  without  definite  form  or  shape; 
a  body  having  two  or  more  different  crystalline 
forms  is  called  polymorpJious.  The  same 
body  always  assumes  the  same  crystalline 
form  under  the  same  conditions,  but  under 


13  DENTAL   CHEMISTRY. 

different  conditions  may  assume  different 
crystalline  shapes,  A  substance  is  said  to  be 
isomorphoiis  with  another  when  it  crystallizes 
in  exactly  the  same  form.  Example:  g-lue  is 
amorphous,  sulphur  is  polymorphous,  sulphate 
of  magnesium  is  isomorphous  with  sulphate  of 
zinc. 

79.  Water  of  Crystallization.— Water  taken 
by  substances  separating  from  solutions  as  a 
necessary  part  of  their  crystals.  Amount  in- 
variable for  same  substance  at  same  temper- 
ature. Example:  each  crystal  of  alum  has  24 
molecules  of  water  to  one  of  alum  itself,  and 
the  formula  of  the  crystal  is  KaAlaCSO*)*. 
24H2O. 

80.  Systems  of  Crystals.— Based  on  imagi- 
nary lines  called  axes  passing  through  the  cen- 
tre of  the  crystal  and  connecting  opposite 
angles  or  opposite  parallel  sides.  For  conven- 
ience, six  systems  of  crystals  may  be  con- 
sidered. 

First  system :  axes  three,  at  right  angles,  equal 
lengths.  Isometric  system.  Forms:  cube, 
octahedron. 

Examples  of  the  first  system  of  crystals: 
native  silver,  chloride  of  silver,  calcium  fluor- 
ide, native  copper,  native  gold. 

Second  system:  axes  three,  right  angles,  one 
longer  or  shorter  than  other  two.  Tetragonal 
or  Dmietric  system.  Form:  right  square  prism. 


PHYSICS.  19 

Example  of  the  second  system:  copper 
pyrites. 

Third  system:  axes  three,  right  angles,  un- 
equal lengths.  Trmietric  or  Orthorkombic 
system.  Forms:  right  rhombic  prism  and 
rhombic  octahedron.  Examples  of  third  sys- 
tem crystals:  sulphates  of  lead,  zinc,  barium, 
magnesium. 

Fourth  system:  axes  three,  unequal,  only 
one  at  right  angles  to  plane  of  other  two. 
Simplest  form:  oblique  rhombic  prism.  Ex- 
amples: borax,  green  vitriol.  Monoclinic 
system. 

Fifth  system:  axes  three,  all  unequal,  and 
all  inclined  to  each  other.  Crystals  compli- 
cated and  apparently  irregular:  rhomboidal 
prism,  acute  and  obtuse  rhombohedrons.  Ex- 
amples: blue  vitriol,  boracic  acid.  Tricliiiic 
system. 

Sixth  system:  four  axes,  three  in  one  plane 
at  angle  of  60°  to  one  another,  fourth  longer 
or  shorter  than  other  three  and  at  right  angles 
to  their  plane.  Example:  quartz.  Hexagonal 
system. 

81.  Chemical  Effects  of  Light. — Many  chemicals  are 
affected  by  exposure  to  light.  Solutions  of  several 
metals,  among  them  silver  and  gold,  throw  down  a  part 
of  the  metal  on  exposure  to  sunlight;  the  latter  has  certain 
rays  capable  of  producing  chemical  changes  and  known 
as  actinic  rays. 

82.    Electricity  due  to  Chemical  Action.— 


20  DENTAL    CHEMISTRY. 

All  chemical  change  produces  electricity. 
This  kind  of  electricity  is  called  voltaic  or  gal- 
vanic, and  is  most  often  developed  by  chemi- 
cal action  between  liquids  and  metals.  Ex- 
ample: when  a  strip  of  copper  and  a  strip  of 
zinc  are  placed  in  dilute  sulphuric  acid,  a  cur- 
rent of  electricity  will  be  found  to  flow  in  a 
wire  connecting"  the  two  strips  of  metal  above 
the  acid.  The  apparatus  is  called  a  galvanic 
element  or  cell. 

83.  Current  of  Electricity. — In  every  gal- 
vanic cell,  the  plates  and  connecting  wires  must 
be  conductors  of  electricity  and  the  liquid  used 
must  be  one  which  will  act  with  greater  vigor 
on  one  of  the  metals  than  on  the  other.  The 
metal  most  actively  attacked  by  the  liquid 
forms  the  positive  or  generating  plate;  the 
other,  the  collecting  or  negative  plate.  The 
current  runs  in  the  liquid  from  the  positive 
plate  to  the  negative;  in  the  wire  connecting  the 
plates  the  current  runs  from  the  negative  plate 
to  the  positive. 

84.  Closed  Circuit. — When  wires  from  the  two  plates 
are  in  contact.     When  not,  the  circuit  is  broken., 

85.  Electrodes. — Endsof  the  wires.  Also  called /><7/^.y. 
The  negative  pole  is  attached  to  the  positive  plate  and 
vice  versa.  Platinum  strips  are  often  fastened  to  the  ends 
of  wires  and  constitute  the  electrodes,  and  the  wires  are 
called  rheophores. 

86.  Oalvanic  Battery.^ A  number  of  galvanic  ele- 
ments so  connected  that  the  current  has  the  same  direc- 


PHYSICS. 


21 


tion  in  all.  Usually  they  are  connected  "in  series",  that 
is,  positive  plate  of  one  element  with  negative  of  the 
next. 

87.  Forms  of  Cells. — Hydrogen  gas  is  generated  by 
the  action  of  an  acid  on  a  metal,  and  the  various  kinds  of 
cells  indicate  the  means  used  by  their  inventors  to  pre- 
vent the  hydrogen  from  accumulating  on  the  negative 
plate. 

Potassium  bichromate  battery:  two  zinc  plates  having 
between  them  a  carbon  plate,  all  hung  in  a  solution  of  po- 
tassium bichromate  in  dilute  sulphuric  acid.  To  make 
the  latter,  pour  167  C.c.  of  sulphuric  acid  into  500  C.c.  of 
water  and  let  the  mixture  cool.  Dissolve  115  grams  of 
potassium  bichromate  in  335  C.c.  of  boiling  water  and 
pour  while  hot  into  the  dilute  acid.  Let  the  whole  cool 
before  using,  [i  gram=i5^  grains  Troy;  30C.  c.=  l 
fluid  ounce].  Chromic  acid  is  formed,  which  destroys 
the  hydrogen.  Zinc  plates  should  be  removed  from  bat- 
tery, when  the  latter  is  not  in  use.  The  zincs  should  be 
amalgamated  by  washing  in  dilute  sulphuric  acid,  then 
pouring  mercury  on  them  while  still  wet  with  the  acid. 
Rub  in  the  mercury  well  and  keep  a  little  of  it  in  the  bot- 
tom of  each  cell. 

The  gravity  battery  is  one  in  which  the  two  solutions, 
zinc  sulphate  and  copper  sulphate,  are  separated,  owing 
to  the  difference  in  their  respective  weights,  the  saturated 
solution  of  copper  sulphate  being  heavier  than  that  of 
the  zinc  sulphate,  when  the  latter  is  in  its  proper  con- 
dition. 

88.  Storage  Batteries. — Are  of  many  forms.  They 
may  be  made  from  any  pair  of  chemical  compounds  un- 
stable in  presence  of  each  other.  They  are  called  also  second- 
ary batteries.  They  have  no  electro-motive  force  of  their 
own,  but  are  capable  of  being  acted  on  by  an  external 
source   of   electricity,  in  such  a  way   as  to   acquire   the 


22 


DENTAL   CHEMISTRY. 


power  to  give  out  an  electric  current,  opposite  in  direction 
to  that  of  the  external  source  by  which  they  are  treated. 
In  some  storage  batteries  the  cell  contains  two  or  more 
large  plates  of  sheet  lead,  and  the  liquid  used  is  dilute 
sulphuric  acid.  A  current  is  passed  through  the  battery, 
and  hydrogen  gas  accumulates  on  one  plate  and  oxygen 
on  the  other.  Disconnect  the  charging  battery  and  a 
current  in  the  opposite  direction  may  now  be  obtained 
from  the  polarized  cell*.  Storage  batteries  are  used  by 
dentists  to  furnish  motive  power  for  the  engine. 

89.  Induced  Current.— Name  given  to  in- 
stantaneous current  produced  in  a  conductor 
by  the  influence  of  a  neighboring-  current  or 
magnet. 

90.  Faradic  Battery. — The  current  induced  in  a  con- 
ductor by  the  influence  of  a  neighboring  current  is  known 
also  as  a  secondary,  interrupted,  or  Faradic  current.  In 
producing  it  an  induction  coil  is  used,  which  is  a  double  coil 
of  wire  wound  around  a  hollow  cylinder  of  wood.  The 
first  or  primary  coil  is  made  of  large,  thick,  copper  wire 
covered  with  silk  or  insulated.  Upon  this  coil,  and  care- 
fully insulated  from  it,  is  wound  the  secondary  coil  of  long- 
er and  thinner  wire.  A  bundle  of  soft  iron  wire  is  inside 
the  inner  coil  to  act  as  a  magnet  whenever  a  current  from 
a  battery  shall  be  sent  through  the  coil.  Before  the  end 
of  the  bundle  of  wires  there  vibrates  a  piece  of  soft  iron 
fastened  to  a  spring.  The  latter  rests  against  a  screw 
which  connects  the  inner  coil  by  a  wire  with  a  galvanic 
battery.  When  a  current  is  sent  through  the  inner  coil, 
an   induced   current  is  produced  in  the   outer  coil  in  the 

♦The  polarization  of  the  plates  is  caused  by  the  accumulation  of 
oxygen  (negative)  on  the  zinc  (positive')  plate,  and  of  hydrogen  (posi- 
tive) on  the  carbon  (negative)  plate.  Owing  to  the  layers  of  gas  on 
each  plate  a  new  or  secondary  current  is  dcvelo.)ed. 


PHYSICS. 


23 


opposite  direction  and  the  bundle  of  soft  iron  wires  is 
magnetized  at  the  same  time.  In  consequence  of  the 
latter  the  hammer  or  soft  iron  in  the  spring  is  drawn  to- 
ward the  bundle  and  the  current  is  thus  broken.  The 
bundle  then  becomes  demagnetized  and  the  hammer  is 
brought  back  to  the  screw  by  the  spring,  the  induced  cur- 
rent now  takmg  the  opposite  direction  to  what  it  did 
when  the  hammer  was  in  contact  with  the  bundle,  and 
so  on.  The  process  is  repeated  as  long  as  the  current 
from  the  battery  is  sent  through  the  primary  coil.  The 
induced  current  is  therefore  a  to  and  fro  current,  or  a  make 
and  break  current,  the  make  current  being  in  opposite  di- 
rection to  the  break.  The  break  currents,  are  the  most 
powerful  and  are  reinforced  by  the  sudden  demagnetiza- 
tion of  the  bundle  or  core  of  iron  wires. 

Qi.  Electrolysis. —  Many  chemical  com- 
pounds in  solution  may  be  decomposed  by  a 
strong  galvanic  current  This  process  is  called 
electrolysis.  Example:  if  a  strong  galvanic 
current  is  passed  through  water  containing  a 
little  sulphuric  acid,  the  water  will  be  decom- 
posed, that  is,  broken  up  into  hydrogen  and 
oxygen  gases,  the  former  being  given  off  at  the 
negative  pole  and  the  latter  at  the  positive. 

92.  Terms  used  in  Electricity. — Circuit:  the  entire 
path  of  the  electrical  current,  including  the  battery  itself, 
and  the  conducting  medium,  which  unites  the  poles. 

Dynamo:  the  dynamo-electric  machine  is  one  in  which 
energy  in  the  form  of  moving  power  is  transformed  into 
energy  in  the  form  of  electricity. 

Electricity. — Different  kinds:  galvanic  electricity,  also 
called  Voltaic,  is  the  term  given  to  electricity  evolved  by 
chemical  action,  as  in  the  bichromate  battery.  It  is  also 
<called  dynamical,  or  current-electricity. 


24  DENTAL   CHEMISTRY, 

Static  electricity  is  that  developed  by  friction. 

Thenno-Electricity  is  that  produced  by  the  agency  of 
heat.  All  metals  are  capable  of  producing  thermo-elec- 
tric currents. 

Magneto-Electricity  is  the  name  given  to  electric  cur- 
rents developed  by  the  relative  movements  of  magnets 
and  wires. 

Potential:  term  used  to  denote  the  degree  to  which  a 
body  is  electrified.  The  electrical  condition  of  the  earth's 
surface  is  taken  as  the  potential  zero  point,  and  all  bodies 
positively  electrified,  are  said  to  have  a  higher  potential 
than  the  earth,  and  all  bodies  negatively  electrified,  to 
have  a  lower  potential.  When  electricity  moves  or  tends 
to  move  from  one  place  to  another,  there  is  said  to  be  a 
difference  of  potential  heUw^Qn  the  two  places. 

Resistance :  term  given  to  the  obstruction  offered  to  the 
passage  of  a  current  by  the  substance  of  the  circuit 
through  which  it  passes.  Silver  offers  the  least  resistance, 
gutta  percha  very  great. 

Electro-motive  force :  term  used  to  indicate  that  property 
of  any  source  of  electricity  by  which  it  tends  to  do  work 
by  transferring  electricity  from  one  point  to  another. 
Ten  cells  have  ten  times  the  electro-motive  force  of  one 
cell. 

Quantity:  as  applied  to  current  electricity,  term  used  to 
mean  the  strength  of  the  current,  or  the  amount  per 
second  acting  to  produce  heat,  magnetism,  etc.  It  is  the 
margin  of  effective  electricity  produced  by  any  battery 
after  the  resistance  of  the  circuit  has  been  overcome. 

Standard  units  of  electrical  measurement:  the  unit  of  elec- 
tro-motive force  is  called  the  volt:  the  Daniell  cell  is  said 
to  have  the  electro-motive  force  of  07ie  volt,  that  is,  the 
electro-motive  force  required  to  produce  a  current  of  the 
strength  of  one  ampere  in  a  circuit  having  a  total  resist- 
ance of  one  ohm.     An  ohm  is  the  unit  of  resistance,  and 


PHYSICS. 


25 


is  approximately  equal  in  resistance  to  that  of  a  wire  of 
pure  copper  one-twentieth  of  an  inch  in  diameter,  and 
two  hundred  and  fifty  feet  long,  or  that  of  one-sixteenth 
of  a  mile  of  No.  g  galvanized-iron  wire  of  ordinary  quality. 
An  ampere  is  the  unit  of  current  strength  and  represents 
the  strength  of  current  passing  in  a  circuit  having  a  total 
resistance  of  one  ohm,  with  an  electro-motive  force  of  one 
volt.  The  coulomb  or  ivcbcr  denotes  the  amount  of  elec- 
tricity which  a  current  of  the  strength  of  one  ampere  can 
furnish  per  second  of  time.  It  is  the  unit  of  quantity. 
li\\^  farad '\s  the  unit  of  capacity  and  represents  the  capa- 
city of  a  condenser  which  contains  one  coulomb  of  elec.- 
tricity  when  the  difference  of  potential  between  its  op- 
posing plates  is  one  volt.  A  microfarad  is  a  millionth  of 
a  farad. 

93.  Ohm's  Law. — The  effective  strength  of  current  in 
any  given  circuit  is  equal  to  the  electro-motive  force  di- 
vided by  the  total  resistance. 

94.  Galvanic  Electricity  in  the  Mouth.— 

Unpleasant  sensations,  from  a  disagreeable 
taste  up  to  a  slight  shock,  are  sometimes  ex- 
perienced by  those  having  metal  in  the  mouth 
either  in  form  of  fillings  or  in  teeth-plates. 
This  is  due  to  the  development  of  galvanic 
electricity  by  contact  with  some  other  metals, 
as  when  pins,  needles,  metallic  tooth-picks,  etc. 
are  touched  to  the  fillings,  or  when  the  clasps 
or  plates  of  artificial  dentures  come  into  contact 
with  fillings,  under  peculiar  conditions  of  oral 
fluids. 

The  fillings  themselves,  especially  if  of  different  metals, 
are  thought  to  be  a  source  of  electricity,  taken  in  connec- 
tion with  the  fluids  of  the  mouth;  effort  has  been  made 


2(5  DENTAL   CHEMISTRY. 

to  explain  the  destruction  of  certain  fillings,  as  due  to  the 
development  of  such  electricity. 
95.    American  Weights  and  Measures : 
apothecaries'  fluid  measure. 

60  minims  (m.)  make  i  fluid  drachm f3 

8  fluidrachms  make  i  fluid  ounce f 3 

16  fluid  ounces  make  i  pint O. 

8  pints  make  i  gallon Cong. 

apothecaries'  weight. 
20  grains  (gr.)  make  i  scruple sc.  or  3 

3  scruples  make  i  drachm dr.  or   3 

8  drachms         make  i  ounce oz.  or  5 

12  ounces            make  i  pound lb.  or  lb 

scale. 

lb.                    oz.                     dr.                     so.  gr. 

I          =         12         =           96         =         288  =  5760 

I        =            8        =          24  =  480 

I         =            3  =  60 

I  =  20 

TROY   WEIGHT. 

24  grains  (gr.)  make  i  pennyweight dwt. 

20  pennyweights  make  i  ounce oz. 

12  ounces  make  i  pound lb. 

SCALE. 

lb.                          oz.                           dwt.  gr. 

I             =            12            =             240  =  5760 

I             =              20  =  480 

I  =  24 

AVOIRDUPOIS   WEIGHT. 

16  drachms  ( dr. )  make  i  ounce oz. 

16  ounces  make  i  pound lb. 

25  pounds  make  i  quarter qr. 

4  quarters  make  l  hundredweight cwt. 

20  hundredweight  make  i  ton T. 


PHYSICS. 

27 

SCALE. 

T.              cwt. 

qr. 

lb. 

oz.               dr. 

I           =         20 

=      80     = 

2000 

= 

32000    =   512000 

I 

=        4     = 

100 

= 

1600    =     25600 

I     = 

25 

= 

400    =       6400 

I 

= 

16    =         256 
I    =           16 

96.    Metric  System : 

MEASURES 

OF  LENGTH. 

I  millimetre 

= 

0.00 1  of  a  metre. 

I  centimetre 

= 

0.0 10  of  a  metre. 

I  decimetre 

= 

o.ioo  of  a  metre. 

1  metre 

=: 

1  metre. 

I  decametre 

= 

10  metres. 

I  hectometre 

= 

100  metres. 

I  kilometre 

= 

1,000  metres. 

I  myriametre 

=z 

10,000  metres. 

MEASURES  OF  SURFACE. 

I  centiare 

= 

I  square  metre. 

1  Are 

= 

100  square  metres. 

I  hectare 

= 

10,000  square  metres. 

MEASURES 

OF  VOLUME. 

I  Cubic  metre 

— 

1,000  < 

Cubic  decimetres. 

1,000  litres,  or  one  kilolitre. 
I  stere. 


MEASURES  OF  CAPACITY. 


I  Litre 


I  milligramme 
I  centigramme 
I  decigramme 
1  gramme 


I  Cubic  decimetre, 

or  1000  Cubic  centimetres. 


MEASURES  OF  WEIGHT. 


0.00 1  of  a  gramme. 
O.oio  of  a  gramme. 
O.IOO  of  a  gramme. 
1  gramme 


28  DENTAL  CHEMISTRY. 

MEASURES  OF  WEIGHT. — Continued. 

I  decagramme  =  lo  grammes. 

I  hectogramme  =  lOO  grammes. 

I  kilogramme  (kilo)  =  looo  grammes. 

I  tonneau  =  lOOO  kilogrammes. 


Metric  Equiralents. 


WEIGHT 


TT  ..     f  .  Approximate  Accurate 

Unit  of  measurement.  equivalent.  equivalent. 

I  gramme  \^\  grains 15.432 

1  grain 0.064  gramme 0.064 

1  kilogramme  (1000  grammes) 2y  pounds,  avoirdupois 2  204 

1  pound,  avoirdupois Yz  kilogramme 0.453 

1  ounce,  avoirdupois  (437>^  grains)  28>^  grammes 28.349 

1  ounce,  troy  or  apothecary  (480  gr.)31  grammes 31.103 

BULK. 

1  Cubic  centimetre 0.06  cubic  inch 0.061 

1  cubic  inch 16>^  Cubic  centimetres 16.386 

1  litre  (1000  Cubic  centimetres) 1  U.  S.  standard  quart 0.946 

1  United  States  quart 1  litre 1 .057 

1  fluidounce 29 >^  Cubic  centimetres ....  29.570 

LENGTH. 

TT^u  ^*.^^-,^.,^^.^««f  Approximate  Accurate 

Umt  of  measurement.  equivalent.  equivalent. 

1  inch 25^  centimetres 2.539 

1  centimetre  (1-lCO  metre) 0.4  inch 0.393 

1  yard 1  metre 0.914 

1  metre  (39.37  inches) 1  yard 1.093 

1  foot 30  centimetres 30.479 

1  kilometre  (1000  metres) %  mile 0.621 

1  mile \'%.  kilometres 1.609 

SURFACE. 

1  hectare  (10,000  square  metres)..  .2K  acres 2.471 

1  acre %  hectare 0.404 

Suppose  we  are  directed  to  use  175  grammes  of  chlo- 
ride of  sodium,  how  much  is  it  in  ounces?  We  see  by  the 
table  that  one  ounce  equals  31  grammes;  divide  175  by 


PHYSICS. 


29 


this,  and  we  have  5.6,  the  required  number  of  ounces.  If 
we  wish  to  measure  53  Cubic  centimetres  of  any  liquid, 
53^29.5,  the  number  of  Cubic  centimetres  in  one  fluid 
ounce,  =1.8  fluid  ounces,  the  required  amount.  Converse- 
ly, suppose  we  have  a  quantity  of  some  chemical  weigh- 
ing three-quarters  of  a  pound,  and  wish  to  find  the  metric 
equivalent.  As  one  pound  is  equal  to  0.453  kilogramme, 
three-quarters  of .  a  pound  will  be  equal  to  three-quarters 
of  that  weight,  or  0.33975  of  a  kilogramme;  or,  as  one  kilo- 
gramme equals  looo  grammes,  three-quarters  of  a  pound 
will  equal  339.75  grammes. 

1.  To  convert  troy  grains  into  centigrammes,  multiply 
by  6. 

2.  To  convert  centigrammes  into  troy  grains,  divide 
by  6. 

3.  To  convert  troy  grains  into  milligrammes,  multiply 
by  60. 

4.  To  convert  milligrammes  to  troy  grains,  divide  by  60. 

5.  To  convert  troy  grains  to  grammes,  or  minims  into 
fluidgrammes,  divide  by  15. 

6.  To  convert  grammes  into  grains,  or  fluidgrammes 
into  minims,  multiply  by  15. 

7.  To  convert  drachms  into  grammes,  or  fluidrachms 
into  fluidgrammes,  multiply  by  4. 

8.  To  convert  grammes  into  drachms,  or  fluidgrammes 
into  fluidrachms,  divide  by  4.    (All  results  approximate), 

97.  Percentage  Solutions. —  In  order  to 
make  a  percentag"e  solution  of  a  solid  in  a 
liquid  both  should  be  weighed.  A  five  per 
cent  solution  by  weight  means  a  solution  100 
parts  of  which  contain  95  parts  by  weight  of 
water  to  5  parts  by  weight  of  the  solid.* 

*It  is  a  common  error  to  suppose  that  a  five  per  cent  solution  is  5 
grains  of  solid  to  100  of  water. 


30  DENTAL    CHEMISTRY. 

Ascertain  the  weight  of  a  bottle,  put  into  it  the  proper 
weight  of  solid  then  add  liquid  enough  to  make  up  the 
final  weight. 

For  example,  suppose  it  is  required  to  make  a  4  per 
cent,  solution  of  cocaine  hydrochlorate:  weight  of  bot- 
tle, 400  grains;  weight  of  bottle  plus  cocaine,  404  grains. 
It  is  evident  that  enough  water  must  now  be  poured  into 
the  bottle,  while  in  the  scale-pan,  to  make  the  final 
weight  500  grains.  Result,  four  grains  of  cocaine  in  nine- 
ty-six of  water,  or  a  four  per  cent  solution. 

Examples:  supposing  weight  of  bottle  to  be  400  grains 
how  would  a  one  per  cent  solution  of  corrosive  sublimate 
be  made?  a  one  in  iooo?f  a  20  per  cent  solution  of  car- 
bolic acid?  Give  total  weights  (bottle  included)  and  the 
weights  of  the  separate  ingredients. 

Answers:  one  grain  of  corrosive  sublimate  and  ninety- 
nine  of  water.  One  grain  of  the  solid  and  nine  hundred 
and  ninety-nine  grains  of  water. 

98.  Specific  Volume. — The  relative  bulks  of  equal 
weights  of  different  bodies  is  their  specific  volume. 
Water  being  taken  as  a  unit,  the  specific  volume  of  any 
substance  is  the  volume  of  a  certain  weight  of  it  com- 
pared to  that  of  an  equal  weight  of  water  at  15°  C. 
(59.6- F.). 

To  find  specific  volume,  divide  the  volume 
of  a  given  weight  of  the  liquid  by  the  volume 
of  an  equal  weight  of  water,  or  divide  the 
specific  gravity  of  water  (which  is  i  or  1000) 
by  the  specific  gravity  of  the  liquid. 

For  example:  what  is  the  specific  volume  of  glycerine? 
100  grains  of  glycerine  measure  84  minims;   100  grains  of 


■fCarefully  notice  the  difference  between  one  in  a  thousand  and  one 
to  a  thousand. 


PHYSICS.  21 

water  measure  105  minims;  84-^105=0.8;  or  1000^-1,250 
(the  sp.  gr.  of  glycerine )  =  0.8oo,  sp.  vol.  of  glycerine.  That 
is,  a  given  weight  of  glycerine  will  only  measure  eight- 
tenths  as  much  as  the  same  weight  of  water. 

99.  To  find  the  volume  of  a  given  weight 
of  water   in  tlie   American   system.—  To 

change  av.  oz.  of  water  to  fi.  oz.  multiply 
by  0.96;  tr.  oz.  of  water  to  fl.  oz.  multiply  by 
1-05;  grams  of  water  to  fl.  oz.  multiply  by 
0.0338. 

Examples:  how  many  fluidounces  in  60  avoirdupois 
ounces  of  water?  how  many  fluidounces  in  10  troy  ounces 
of  water?  how  many  fluidounces  in  20  grams  of  water? 

Answers:  60X0.96.  10 X  1.05.  20x0.0338. 

100.  To  find  the  volume  of  a  given  weight 
of  any  liquid. — Multiply  the  volume  of  an 
equal  weight  of  water  by  the  specific  volume 
of  the  liquid;  or  divide  the  volume  of  an  equal 
weight  of  water  by  the  sp.  gr.  of  the  liquid. 

Examples:  how  many  fluidounces  in  200  troy  ounces  of 
nitric  acid?  200  troy  ounces  of  water  are  (200X1.05) 
fluidounces,  or  210  fluidounces  (see  previous  rule).  210 
multiplied  by  the  specific  volume  of  nitric  acid,  O.704, 
(found  by  dividing  the  specific  gravity  of  the  water  by  the 
specific  gravity  of  the  acid,  1.42)  will  give  147.8,  which  is 
number  of  fluidounces  required. 

loi.  To  find  the  weight  of  a  given  volume 
of  water. — Fluido  unces  to  avoirdupois  ounces, 
divide  by  0.96;  fluidounces  to  troy  ounces,  di- 
vide by  1.05;  fluidounces  to  grams,  divide  by 
0.0338. 

Examples:    what  is  the   weight  of    13  fluidounces    of 


32  DENTAL   CHEMISTRY. 

water?  of  a  pint  of  water?  of  three  pints?    (Give  answers 
in  both  avoirdupois  and  troy). 

Answers:  13-4-0.96.  13-M.05.  16-^0.96.  16-M.05.  Three 
times  the  third  and  fourth  answers. 

102.  To  find  the  weight  of  a  given  volume 
of  any  liquid.— Divide  the  weight  of  an  equal 
volume  of  water  by  the  sp.  vol.  of  the  liquid, 
or  multiply  the  weight  of  an  equal  volume  of 
water  by  the  sp.  gr.  of  the  liquid. 

Example:  find  the  weight  (troy)  of  200  fluidounces  of 
nitric  acid  of  sp,  gr.  1.42.  The  weight  troy  of  200  fluid- 
ounces  of  water  is  200-^  1.05  or  190.4.  Divide  this  by  the 
specific  volume  of  nitric  acid,  which  is  0.704,  and  we  have 
270.4,  which  is  the  weight  required  in  troy  ounces. 

103.  Thermometry.— The  Centigrade  ther- 
mometer has  its  zero  at  the  freezing  point  and 
its  boiling  point  at  100°,  the  number  of  inter- 
vening degrees  being  100.  One  degree  Centi- 
grade equals  1.8°  of  Fahrenheit.  To  convert 
Centigrade  to  Fahrenheit  multiply  by  1.8  and 
add  32.  To  convert  Fahrenheit  to  Centigrade 
subtract  32  and  multiply  by  9. 


Examples:  Convert  60°  Centigrade  to  the  correspond- 
ing Fahrenheit.  60  times  1.8  equals  108.  The  latter 
plus  32  equals  140.  [Turning  to  the  table  on  page  31,  we' 
find  60°  C.  equals  140°  F].  Now  find  what  degree  Centi- 
grade corresponds  to  770°  Fahrenheit.  770  less  32  equals 
738.  The  latter  multiplied  by  i equals  410.  [Consulting 
the  table  on  page  33,  we  find  770°  F  equals  410°  C] 

In  general  it  is  easier  to  consult  the  table  if  the  latter 
is  at  hand  when  wanted,  but  as  such  is  not  always  the 
case  it  is  advisable  to  become  familiar  and  ready  with  the 
rule. 


33 


Comparison  of  Centigrade 

AND  Fahrenheit  Degrees.* 

Cent. 

Fahr. 

Cent. 

Fahr. 

Cent. 

Fahr. 

Cent. 

Fahr. 

—40 

—40.0 

—5 

+23.0 

+30 

+86.0 

+  65 

+149.0 

39 

38.2 

4 

24  8 

31 

87.8 

66 

15C.8 

38 

36.4 

3 

26.6 

32 

89.6 

67 

152.6 

37 

34  6 

—  2 

28.4 

33 

91.4 

68 

164.4 

36 

32.8 

—1 

30  2 

34 

932 

69 

156.2 

35 

31.0 

0 

32.0 

35 

95.0 

70 

168.0 

34 

29.2 

-fl 

.       33.8 

36 

96.8 

71 

159.8 

33 

27.4 

2 

35.6 

37 

98.6 

72 

161.6 

32 

25.6 

3 

37.4 

38 

100.4 

73 

163.4 

31 

23.8 

4 

39.2 

39 

102.2 

74 

16.5.2 

3(i 

22.0 

6 

41.0 

40 

104.0 

76 

167.0 

29 

20.2 

6 

42.8 

41 

105.8 

76 

168.8 

28 

18.4 

7 

4t.6 

42 

107.6 

77 

170.6 

27 

16.6 

8 

46.4 

43 

109.4 

78 

172.4 

2« 

14.8 

9 

48.2 

44 

111.2 

79 

1 74.2 

25 

13.0 

10 

50.0 

45 

113.0 

80 

176.0 

24 

11.2 

11 

51.8 

46 

114.8 

81 

177.8 

23 

9.4 

12 

63  6 

47 

116.6 

82 

179.6 

22 

7.6 

13 

55.4 

48 

118.4 

83 

181.4 

21 

5.8 

14 

57.2 

49 

120.2 

84 

183.2 

20 

4.0 

15 

.59.0 

50 

122.0 

85 

185  0 

19 

2.2 

16 

60.8 

51 

123.8 

86 

186.8 

18 

—0.4 

17 

62.6 

52 

126.6 

87 

188.6 

17 

+1.4 

18 

64.4 

53 

127.4 

88 

190.4 

16 

3.2 

19 

66.2 

64 

129.2 

89 

192.2 

15 

5.0 

20 

68  0 

55 

1310 

90 

194.0 

14 

6.8 

21 

69.8 

66 

132.8 

91 

195.8 

13 

S.6 

22 

71.6 

.17 

134.6 

92 

197.6 

12 

10.4 

23 

73.4 

68 

136.4 

93 

199.4 

11 

12.2 

24 

75.2 

59 

138.2 

94 

201.2 

10 

14.0 

25 

77.0 

60 

J  40.0 

95 

203.0 

9 

1.5.8 

26 

78.8 

61 

141.8 

96 

204.8 

8 

17.6 

27 

80.6 

62 

143.6 

97 

206.6 

7 

19.4 

28 

82.4 

-^63 

145.4 

98 

208.4 

— G 

+2i.2 

+29 

+84.2 

64 

+147.2 

+     99 
+  100 

+  210.2 
212.0 

110 

-f  2.30 

+210 

+410 

+310 

+690 

410 

770 

120 

248 

220 

428 

320 

608 

420' 

788 

130 

266 

230 

446 

330 

626 

430 

806 

140 

284 

240 

464 

340 

644 

440 

824 

150 

■     302 

2.50 

482 

350 

662 

450 

842 

160 

320 

260 

500 

360 

680 

460 

860 

170 

338 

270 

518 

370 

698 

470 

878 

180 

3.56 

280 

536 

380 

716 

480 

896 

+  190 

374 

290 

554 

390 

7.34 

490 

+914 

4-200 

+392 

+300 

+572 

+400 

762 

+  500 

+  932 

+500 

+932 

+800 

1472 

+1100  +2012 

4-1400 

2552 

600 

1112 

+900 

+16.52 

1200 

2192 

ir-oo 

2732 

+700  +1292 

+  1000  +1832 

+  1300  +2372 

+1600 

+2912 

*  Barker. 


34  DENTAL   CHEMISTRY. 


CHAPTER  II* 

CHEMICAL    PHILOSOPHY. 

104.  Chemistry  defined.— Chemistry  is  the 
science  which  studies  the  properties,  constitu- 
tion, and  laws  of  composition  of  bodies, 
whether  crystaUine,  volatile,  natural,  of  artificial. 

105.  Field  of  chemistry.— Chemistry  studies  such 
properties  of  matter  as  result  from  its  atomic  composition. 

Cheinical  Philosophy  treats  of  the  general 
facts  of  chemistry,  the  general  laws  deduced 
from  these  facts,  and  the  operations  which  lead 
to  a  knowledge  of  the  internal  composition  of 
matter.  It  comprises  and  classifies  our  knowl- 
edge of  those  phenomena  which  imply  a 
change  of  substance. 

Special  Chcviistry  studies  the  character  and  properties  of 
certain  definite  bodies,  and  shows  in  what  manner  they 
are  governed  by  the  laws  of  general  chemistry,  or  chemi- 
cal philosophy. 

106.  Analysis  and  Synthesis.  —  Chemical 
analysis  is  an  operation  by  which  the  composi- 
tion of  matter  is  ascertained  by  splitting  up  a 
substance  and  separating  its  constituents  from 


*The  student  must  thoroughly  master  the  contents  of  Chapter  II 
up  to  Section  148  before  attempting  the  laboratory  work  of 
Chapter  VI. 


CHEMICAL    PHILOSOPHy. 


35 


one  another.  Synthesis  is  an  operation  by 
which  simple  bodies  are  combined  to  form 
compound  ones,  or  compounds  combined  to 
form  complex  ones. 

107.  Definitions-Molecule,  Atom,  Element,  {l,w\\- 
^QViwA.— Matter  or  substance  is  the  general  term  given  to 
that  which  has  length,  breadth,  and  thickness.  Any  por- 
tion of  matter  which  we  perceive  by  the  senses  is  called  a 
inassoi  matter.  Every  mass  of  matter  consists  of  molecules. 
A  Molecule  is  the  smallest  particle  into  which  any  sub- 
stance can  be  divided  without  losing  its  identity  as  that 
substance.  The  smallest  particle  into  which  common  salt 
can  be  divided  and  still  be  salt  and  nothing  but  salt,  is 
termed  a  molecule  of  salt.  The  smallest  particle  of  iron 
which  can  exist  free,  that  is,  uncombined  with  anything 
else,  is  called  a  molecule  of  iron.  Molecules  are  too 
small  to  be  seen  even  with  the  aid  of  the  most  powerful 
microscope.  Their  existence,  however,  is  now  very  gener- 
ally admitted,  as  we  are  able  to  account  for  numerous 
phenomena  if  we  assume  that  molecules  exist.  When  a 
substance  loses  its  identity,  its  molecules  split  up  into 
small  particles  called  atoms,  which,  however,  have  an  at- 
traction for  one  another  and  tend  to  form  new  molecules 
b\'  coming  together  in  groups.  Thus,  the  molecule  of 
mercuric  oxide  is  composed  of  an  atom  of  mercury  com- 
bined with  an  atom  of  oxygen;  when  this  substance  is 
heated,  its  molecules  break  up,  and  the  substance  is  no 
longer  the  oxide  of  rnercury,  but  mercury  and  oxygen. 
When  the  molecules  of  oxide  of  mercury  split  up,  the 
constituent  atoms  re-arrange  themselves,  those  of  the 
mercury  forming  molecules  of  mercury,  and  those  of  oxy- 
gen molecules  of  oxygen. 

The  molecule,  then,  is  composed  of  atoms,  held  to- 
gether by  a  certain  attraction  called  by  some  chemism,  by 


36  DENTAL    CHEMISTRY. 

others  chemical  affitiity.  Each  atom  has  an  attractive 
power  for  other  atoms,  which  is  definite  in  quantity  but 
neutralized  when  a  sufficient  number  of  other  atoms  ap- 
proach it. 

Definition  i.  A  molecule  is  the  smallest 
particle  of  any  substance  which  can  exist  by 
itself  and  remain  free  and  uncombined.  Mole- 
cules are  destructible  and  divisible. 

Definition  2.  An  atom  is  the  still  smaller 
particle  entering^  into  the  composition  of  the 
molecule.  Atoms  cannot,  in  all  probability,  re- 
main free  and  uncombined;  they  are  indestruc- 
tible and  indivisible. 

It  follows  from  definition  2,  that  matter  is 
indestructible. 

Definition  3.  Element:  a  substance  whose 
molecules  are  composed  of  the  same  kind  of 
atoms,  as  the  molecules  of  §:old;  the  molecules 
of  any  substance  in  Table  i  are  composed  of 
atoms  of  that  substance,  and  of  nothing  else. 

Definition  4.  Compound:  a  substance  whose 
molecules  are  composed  of  different  kinds  of 
atoms.  The  molecule  of  salt  is  not  composed 
of  atoms  of  sodium  alone,  nor  of  chlorine 
alone,  but  of  an  atom  of  sodium  and  an  atom 
of  chlorine. 

Definition.  5.  Mixture:  two  or  more  sub- 
stances form  a  Mixture  when  the  particles  of 
one  are  scattered  throughout  those  of  the  other 
or  others,  without  any  change  taking  place  in 


CHEMICAL    PHILOSOPHY.  37 

the  chemical  or  specific  properties  of  one  or  the 
other.     Example:  sand  and  sugar. 

1 08.  Law  of  Avo^'adro.— Equal  volumes  of 
all  bodies  in  the  state  of  gas  and  at  the  same 
temperature  and  pressure  contain  the  same 
number  of  molecules.  Therefore  (a)  the  mole- 
cules of  all  bodies  in  the  gaseous  state  are  of 
the  same  size  and  (<$>)  the  weight  of  any  mole- 
cule, as  compared  with  that  of  hydrogen,  is  in 
proportion  to  the  weight  of  any  volume  given, 
as  compared  with  the  same  volume  of  hydro- 
gen, 

109.  How  to  (leteriiiiiie  the  number  of  atoms  in  the 
hydrogen  molecule. — Suppose  a  given  volume  of  hydro- 
gen contains  10,000.000  molecules;  byAvogadro's  law  the 
same  volume  of  chlorine  will  contain  10,000,000  mole- 
cules. Combined,  they  form  /zvo  volumes  of  hydrochloric 
acid  gas  Vthich  will  necessarily  contain  20,000,000  mole- 
cules. Analysis  shows  each  molecule  of  hydrochloric 
acid  gas  to  consist  of  two  atoms,  one  of  hydrogen  and 
one  of  chlorine,  that  is,  the  20,000,000  molecules  of  hydro- 
chloric acid  gas  will  contain  20,000,000  atoms  of  hydro- 
gen and  20,000,000  of  chlorine.  Now  there  were  but  10.- 
000,000  molecules  of  hydrogen  in  the  start,  before  com- 
bination, therefore  each  molecule  of  hydrogen  must  have 
contributed  two  atoms  of  hydrogen.  So  also  with  the 
chlorine. 

From  this  it  follows  that  there  are  two  atoms  in  every 
molecule  of  hydrogen;  and  the  weight  of  the  atom 
(atomic  weight)  of  hydrogen  being  taken  as  i,the  weight 
of  its  molecule  (molecular  weight)  will  be  2. 

1 10.  Symbols. —  Chemists  designate  each 
element  by  an  abbre\iation  called  a  Symbol, 


38  DENTAL    CHEMISTRY. 

which  is  often  the  first  letter  or  first  two  letters 
of  its  Latin  name. 

Thus  the  symbol  for  potassium  is  K  (Latin  Kalium) 
that  of  gold  Au  ( Latin  Aurum). 

A  symbol  not  only  designates  an  element 
but  just  one  atom  of  that  element  having  a 
definite  weight  (atomic  weight). 

Thus  O  not  only  signifies  oxygen,  but  o/u'  atom  of  oxy- 
gen, or  i6  parts  by  weight  of  oxygen. 

The  symbols  of  the  elements  with  the  atomic  weights, 
specific  gravity,  specific  heat,  and  melting  point  are  now 
shown  by  Table  i. 

The  beginner  should  pay  particular  attention  to  those 
elements  printed  in  large  type.  Note  that  the  metals,  as 
a  rule,  are  positive  to  hydrogen,  while  the  non-mctah^  are 
negative  to  it.  Observe  that  hydrates  of  elements  at  the 
positive  end  form  bases,  while  hydrates  of  those  at  the 
negative  end  form  acids. 

Table  i  is  that  of  Professor  W.  H.  Seaman,  M.  D.  The 
atomic  weights  are  from  the  "Laboratory  Yearbook"  of 
Professor  John  Howard  Appleton,  as  are  also  forty  of  the 
figures  of  specific  gravity.f 

*Antimony  resembles  metals  in /^/yjzVa/  properties  not  chemical. 

tThe  forty  are  those  of  Li,  K,  Na.  CI,  Ca.  Mg,  P,  S,  Gl,  C,  Si,  Al, 
Sr,  Br,  I,' As,  Te,  Sb.  Cr,  Zn.  Sn.  Fe,  Mn,  Co,  Ni,  Cd,  Mo,  Cu,  Bi,  Ag, 
Rh.  Pb.  Pd,  Hg,  W,  U,  Au,  Pt,  Ir. 

Those  who  intend  to  pursue  the  study  of  chemistry  more  in  detail 
will  do  well  to  read  Lothar  Meyer  s  work  on  Theoretical  Chemistry, 
or  Remsen's  book  entitled  "The  Principles  of  Theoretical  Chemistry." 
Among  other  works  on  chemistry  of  general  value  are  those  of 
Beilstein,  Roscoe,  and  Schorlemmer,  Jungfleisch.  For  an  elementary 
work,  Nichors  "Abridgment"  of  Eliot  and  Storer  is  satisfactory;  the 
beginner  will  find  the  appendix  valuable  in  its  instructions  about 
chemical  manipulations. 


Table  i. 
Constants  of  the  Elements. 

(  Arranged  by  Prof.  Seaman.) 

Electro-Chemical  Series. 


39^ 


Positive  end:  hydrates 
form  bases. 


NAME. 


Perissad  Artiad 


Ccesium 

Rubidium 

POTASSIUM  (Kalium)... 

SODIUM  (Natron) 

LITHIUM 

BARIUM  

STRONTIUM 

CALCIUM 

MAGNESIUM 

Glucinum  (Beryllium,  Be) 

Yttrium 

Erbium 

ALUMINIUM 

Zirconium 

Thorium 

CERIUM ,.... 

Didymium 

Lanthanum 

MANGANESIUM 

Gallium 

ZINC 

IRON(Ferrum) 

NICKEL 

COBALT 

Thallium 

CADMIUM 

LEAD  (Plumbum) 

Indium 

TIN  (Stannum) 

BISMUTH 

Uranium 

COPPER  (Cuprum) 

SILVER  (Argentum) 

MERCURY  (Hydrargyrum) 

Palladium 

Ruthenium 

Rhodium 

PLATINUM 

Iridium 

Osmium 

GOLD  (Aurumj 

HYDROGEN 

SILICON 

Titanium 

Cnlumbium  (Niobium  Nb) 

Tantalum 

Tellurium 

ANTIMONY  (Stibium)... 
CARBON 


BORON 

Wolfram  (Tungsten). 

Molybdenum 

Vanadium 

CHROMIUM 

ARSENICUM 

PHOSPHORUS 

Selenium 

IODINE 

BROMINE.. 

CHLORINE 

Fluorine 

NITROGEN 

SULPHUR 

OXYGEN 


SYMBOLS. 


Cs 
Rb 
K 

Na 
Li 


Y 
E 
Al 


D 
La 


Ga 


Tl 


Ag 


Au 
H 


Cb 
Ta 


Sb 


As 
P 


I 

Br 
CI 
F 

N 


Ba 

Sr 
Ca 
Mg 

g1 


Zr 

Th 
Ce 


Mn 

Zn 
Fe 
Ni 
Co 

Cd 
Pb 

Sn 

U 
Cu 

?I 

Ru 
Rh 
Pt 
Ir 
Os 


Te 


W 

Mo 


Cr 


Se 


Atomic 
weights. 


Approx 
Atuinic 
wght 


132.5830 

85  2510 

39.01911 

22  99b0 

7.0073 

136.7630 

87.3.40 

39.9900 

23.9590 

9.0850 

89.8160 

165.8910 

27.0090 

>■  9.3670 

233.4140 

140.4240 

144.5730 

138.52fiO 

53.9060 

68.8540 

64  9045 

55.9J30 

57.9280 

58.8870 

203.7150 

111.8350 

206.4710 

113.3980 

117.6980 

207.5230 

238.4820 

63.1730 

107.6750 

l<J9.71v!0 

105.7370 

104.2170 

104.0.550 

194.4150 

191.6510 

198.4940 

196.1550 

1.0000 

28.1950 

47.9997 

93.8120 

182.1440 

127.9fi00 

119.9550 

11.9736 

10.9410 
183.6100 
95.5270 
51.2560 
52.0090 
74.9180 
30.9580 


132.6 

85.3 

39.0 

23.0 

7.0 

136.8 

87.4 

40.0 

24.0 

9.1 

89.8 

165.9 

27.0 

89.4 

233.4 

140.4 

144.6 

138.5 

63.9 

68.9 

f4.9 

55  9 

57.9 

58.9 

203.7 

111.8 

206.5 

113.4 

117.7 

207.5 

23S.5 

63.2 

1(17.7 

199.7 

105.7 

104.2 

104  1 

194.4 

192.7 

198.5 

196.2 

1.0 

28.2 

48.0 

93.8 

182.1 

128.0 

120.0 

12.0 

10.9 
183.6 
95.5 
51.3 
52.0 
74.9 
31.0 


78.7970  78.8 


126.5570 
79  7680 
35.3700 
18.y840 
14.0210 
31.9840 
16.9633 


126  6 
79.8 


Speciticgravlty 
(Water=l) 


1.88 

1.52 

0.86 

0.97 

0.59 

4  00 

2.54 

1.5H 

1.70  to  1.74 

2.10 

4.80 


Specific  Heat. 


2  50  to  2, 

4.10 

7, 90 

6.62 

6.40 

6.10 

8  01  to  8. 
6.00 

7.10  to  7. 
7.79  to  7 
8.60  to  8. 
8.49  to  8. 

11.80 

8.45  to  8. 
11.33  toll. 

7.40 

7.30 

9  80 
18.40 

8.93  to  8. 
10  4(1  tolO. 
13.G0 
11.80 
11.40 

11.00  toll. 
21.50 
21.80 
22.40 
19.20  tol9. 


2.49 

7.10 
10.78 

6.18  to  6.24 
6.72 

2.27  to  3.52 

2  63 
17.20  to  18.30 

8.62  to  8.64 
5.50 

7.01 

5.63  to  5.67 
1.83  to  1.96 

4.28  to  4.80 


0.169.'; 
0.2934 
0.9408 


0.2143 


0.1217 

0.0955 
0.1138 
0.1086 
0.1069 
0.0338 
0.0556 
0.0314 

0.0562 
0.0308 
0.0619 
0.09ol 
0.0570 
0.0319 
0.0592 

0.0562 
0.0324 
0.0325 
0.0311 
0.0324 
3.4090 
0.1774 


4.95 

2.99  t'l  3.19 
35  4  1..33(liquia)  0.1210 
19  0 

'O  2438 

1.98  to  2.07  0.1776 

,0.2175 


0.0473 
0.0557 
0,1468  toO.2415 

0.2500 
0.0334 
0.0721 

0.0814 
0.1887 
0.0746 

0.0541 
0.0813 


14  0 
32  0 
16  0 


NEGATIVE  END:     hydrates  form  acids. 


40  DENTAL    CHEMISTRY. 

Such  elements  as  neptunium,  davyum,  phillipium.  deci- 
pium,  etc.,  etc.,  are  of  no  importance  to  the  dentist- 
Moreover,  Crookes,  in  his  address  to  the  Chemical  So- 
ciety of  Great  Britain,  has  questioned  the  elementary 
character  of  the  so-called  rare  earths  and  proposes  the 
term  "meta-elements"  for  those  substances  which  are 
neither  compounds,  mixtures,  nor  elements. 

III.  Number  of  Atoms  in  Molecules  of  Elements. — 
At  ordinary  temperatures  most  of  the  elements  given  in 
Table  i  contain  two  atoms  in  the  molecule  and  are  called, 
therefore.  Diatomic.  Exceptions:  mercury,  cadmium, 
zinc,  barium  are  Monatomic,  /.  e.,  have  one  atom  in  the 
molecule;  ozone  contains  three  atoms  of  oxygen;  the 
molecule  of  phosphorus  and  of  arsenic  contains  four  atoms; 
that  of  sulphur,  six,  but  at  high  temperatures,  two. 

Elemental  Atoms  and  Molecules. — The  symbols 
given  in  Table  i  should  not  be  used  to  represent  the  ele- 
ments in  general;  each  symbol  represents  one  atom  of 
the  element;  thus,  Zn  does  not  represent  zinc  in  general, 
but  one  atom  of  the  element  zinc  with  the  properties  of 
that  atom,  namely,  definite  unchanging  weight  and  defi- 
nite power  of  attraction  for  other  atoms. 

Rule  1.— To  Denote  a  K^umber  of  Atoms  of 
an  Element,  write  the  Symbol  of  the  Ele- 
ment with  the  required  number  in  Arabic 
Figures  at  the  lower  riglit  liand  corner  of 
the  Symbol. — Ziia  means  two  atoms  of  zinc; 
H3  means  three  atoms  of  hydrogen ;  O4  means 
four  atoms  of  oxygfen.  Where  one  atom  of  an 
element  is  to  be  represented,  write  the  symbol 
only. 

Rule  2.— To  Denote  a  Molecule  of  an  Ele- 
ment, write  the  Symbol  of  that  Element  witli 


CHEMICAL    PHILOSOPHY, 


41 


the  Figure  2  at  its  lower  right  hand  cor- 
ner.—Exceptions:  write  the  symbols  only  of 

mercury,  cadmium,  zinc,  and  barium;  write 
four  after  the  symbols  of  phosphorus  and 
arsenic,  and  six  after  sulphur.  O2  means  one 
molecule  of  oxygen,  composed  of  two  atoms. 
Hg"  means  one  molecule  of  mercury,  composed 
of  one  atom;  P4  means  one  molecule  of  phos- 
phorus, composed  of  four  atoms;  Se  means  one 
molecule  of  sulphur,  composed  of  six  atoms. 
(See  III  for  Atomicity). 

Rule  3.— To  Denote  a  Number  of  Molecules 
of  an  Element,  write  the  required  Number 
as  a  full  sized  Figure  before  the  expression 
for  one  Molecule.  2O2  means  two  molecules 
of  oxygen,  each  composed  of  two  atoms.  2Zn 
means  two  molecules  of  zinc,  each  composed 
of  one  atom. 

112.  Atomic  weight. — The  atomic  weight 
of  an  element  denotes  the  weight  of  an  atom 
of  it  referred  to  the  weight  of  an  atom  of  hy- 
drogen as  unity. 

The  proportions  in  which  atoms  combine  also  represent 
the  weights  of  the  atoms:  thus,  oxygen  unites  with  other 
elements  in  proportions  of  i6,  therefore  i6  is  the  weight 
of  the  atom  of  oxygen. 

113.  Determination  of  atomic  weight. — By  quanti- 
tative analysis  the  weights  of  two  elementary  substances 
forming  a  compound  is  ascertained.  The  proportion  of 
these  weights,  one  to  another,  will  be  either  the  ratio  of 
the   atomic    weights  of  the   two  elements,  or  else  that 


42  DENTAL  CHEMISTRY. 

of  some  simple  multiple,  the  latter  being  previously  known 
from  a  comparison  of  the  compounds  of  the  element  whose 
weight  we  are  seeking.  Thus,  suppose  it  is  desired  to 
find  the  atomic  weight  of  zinc.  Suppose  that  on  using  a 
given  weight  of  zinc  and  of  hydrochloric  acid  a  certain 
volume  of  hydrogen  is  evolved.     Make  a  proportion: 

Weight  of  hydrogen  found:  weight  of  zinc  used  =  i:  x. 
Now  X  will  be  either  the  atomic  weight  of  zinc,  or  some 
multiple  of  it.  From  a  comparison  of  the  numerous  zinc 
compounds  we  know  the  result  obtained  to  be  half  the 
atomic  weight.  Double  the  value  to  find  the  accepted 
weight. 

114.  Quality  of  Coiiibiniiig  Power  of 
Atoms.    Positive  and  Negative  Elements.— 

When  a  current  of  electricity  of  sufficient 
strength  is  passed  through  a  chemical  com- 
pound in  state  of  solution,  /.  e.,  dissolved,  the 
compound  is  broken  up  into  its  constituent  ele- 
ments. Of  these  elements  some  are  found  at 
the  positive  pole  of  the  battery,  others  collect 
at  the  negative. 

An  element  attracted  to  the  positive  pole  is  called  a 
negative  element;  one  attracted  to  the  negative  pole  dL posi- 
tive element.  Elements  are  not  absolutely  positive  or 
negative  but  only  relatively  so,  i.  e.,  with  reference  to  one 
another.  In  Table  1  the  list  of  elements  is  so  arranged 
that  each  element  is  negative  to  the  one  below  it  and  positive 
to  the  one  above  it.  For  example,  suppose  it  be  required 
to  know  which  of  the  two  elements,  sulphur  and  oxygen, 
is  positive  to  the  other  and  which  negative.  Consulting 
Table  1,  it  will  be  found  that  oxygen  is  written  beloio  sul- 
phur, therefore  negative  to  it;  sulphur  is  written  above 
oxygen,  therefore  positive  to  oxygen. 


CHEMICAL    PHILOSOPHY. 


43 


115.    Quantity  of  combining  power  of  Atoms.* — One 

atom  of  an  element  does  not  necessarily  combine  with,  or 
take  the  place  of,  one  atom  of,  another  element.  It  may 
unite  with  i,  3,  or  5  atoms  of  another  element,  or  with  2, 
4,  or  6  atoms  of  it.  An  atom  of  bromine  for  example  may 
combine  with  one  atom  of  hydrogen,  but  an  atom  of  oxy- 
gen requires  two  of  hydrogen,  one  of  nitrogen  requires 
tlircc  and  so  on. 

.   The  equiyalence  or  qiiantivalence  of  an 

atom  of  an  element,  by  which  we  mean  the 
quantity  of  combining  power  which  it  has,  is 
expressed  as  i,  2,  3,  4,  5,  6,  or  7,  according-  as 
the  atom  will  attach  to  itself,  or  be  exchanged 
for,  I,  2,  3,  4,  5,  6,  or  7  atoms  of  hydrogen,  or 
the  equivalent  of  those  atoms. 

If  the  atom  combines  with  one  atom  of  hydrogen,  or 
exchanges  for  one  atom  of  hydrogen,  it  is  called  a  Monad, 
if  with  two  a  Dyad,  if  with  three  a  Triad,  if  with  four  a 
Tetrad,  if  with  five  a  Pentad,  if  with  six  a  Hexad,  if  with 
seven  a  Heptad.  Monads  are  equivalent  to  monads, 
dyads  to  dyads,  etc.  Dyads  are  equivalent  to  two  mon- 
ads, triads  to  three  monads,  etc.  One  monad  and  one 
dyad  are  together  equivalent  to  one  triad,  etc. 

The  following  table  should  now  be  carefully  committed 
to  memory: 

Table  2.  QuANTivALENCE.f 

Monads.  Dyads.  Triads. 

Potassium.  Barium.  Bismuth. 

Sodium.  Calcium.  Gold. 

*The  terms  quantivalence,  equivalence,  equivalency,  and  valence 
are  all  used  to  denote  the  quantity  of  the  combining  power  of  atoms. 

tThe  elements  are  arranged  in  electro-chemical  order,  beginning 
with  the  positive  and  ending  with  the  negative  or  least  positive. 


44 


dextal  chemistry. 


Table  2. — Continued. 


Lithium. 

Silver. 

Hydrogen. 

Iodine. 

Bromine. 

Chlorine. 

Fluorine. 

Tetrads. 

Aluminium, 

Tin. 

Platinum. 

Silicon. 

Carbon. 


Magnesium. 

Zinc. 

Lead. 

Copper. 

Mercury. 

Sulphur. 

Oxygen. 


Antimony. 

Boron. 

Arsenic. 

Phosphorus. 

Nitroeen. 


Hexads. 
Manganese. 
Iron. 
Chromium. 


Notice  that  those  '\vi-ine  are  all  monads,  that  the  gases 
hydrogen,  oxygen,  nitrogen  are  monad,  dj-ad,  and  triad 
respectively. 

Monads  are  said  to  be  univalent. 


Dyads 

"         " 

bivalent. 

Triads 

<(         t< 

trivalent. 

Tetrads 

<t         11 

tetravalent. 

etc., 

etc. 

etc. 

4.      To 

express 

the    Eqiiiy 

alence 

Rule 

( Quail tiyalence)  of  an  Atom,  place  a  Roman 
Numeral  above  and  to  the  right  of  the  Sym- 
hoL 

O'  means  one  atom  of  oxygen  having  2  as  its  quanti- 
valence,  or  equivalence  as  it  is  often  called.  N  means 
one  atom  of  nitrogen  having  3  as  its  equivalence. 

N.  B,--Quantivalence  is  sometimes  expressed  by  dashes, 


CHEMICAL    PHILOSOPHY. 


45 


thus:  O",  N"';  by  some  the  points  of  attraction,  or  bonds, 

of  an  atom  are  expressed  as  follows: 

Monad  O — {^^^  bond).  |  \  / 

Tetrad  — Q —  (four  bonds).     Hexad — Q — 
Dyad —O— (two  bonds).  |  /    \ 

I  \  I  /  \  I  / 

Triad —Q— (three  bonds).    Pentad     Q     (etc.).  Heptad  — Q— 

/  \  /    \ 

1 16.  Variations  in  Quantivalence. — Unfortunately  for 
the  learner,  the  various  elements  do  not  always  adhere  to 
the  quantivalence  established  in  Table  2.  Certain  of  the 
elements  are  not  only  of  the  quantivalence  of  Table  2, 
but  of  other  quantivalence  also. 

This  is  the  most  difficult  thing  in  chemical  theory  for 
the  beginner  to  understand.  It  has  been  found  by  analy- 
sis that  nitrogen,  for  example,  is  sometimes  a  monad, 
sometimes  a  triad,  and  sometimes  a  pentad.  This  is  be- 
cause one  element  may  form  several  different  compounds  • 
with  another  element. 

Let  the  student  now  commit  to  memory  the  following 
table: 

Table  3. — Variations  in  Quantivalence. 

List  I. — Elements  often  either  Monads,  Triads,  or  Pentads. 

Chlorine I,  III,  V. 

Bromine I,  III,  V. 

Iodine I,  III,  V. 

Nitrogen I,  III,  V. 

Phosphorus —  I,  III,  V. 

Arsenic I,  III,  V. 

List  LI. — Elements  often  either  Triads  or  Pentads. 

Antimony Ill,  V. 

Bismuth Ill,  V. 

List  ILL. — Elements  often  either  Dyads  or  Tetrads. 

Carbon II,  IV. 


46  DENTAL   CHEMISTRY. 

Silicon II,  IV. 

Tin II,IV. 

Lead II,  IV. 

Platinum II,  IV. 

List  IV.— Elements  often  either  Dyads,  Tetrads,  or  Hcxads. 

Sulphur II,  IV,  VI. 

Selenium II,  IV,  VI. 

Other  elements  varying  in  quantivalence  will  be  noticed 
whenever  necessary.  Table  3  includes  the  most  import- 
ant variations.  It  must  be  noticed  that  the  equivalence 
of  an  atom  always  increases  or  diminishes  by  two;  thus, 
chlorine  may  be  either  I,  III,  or  V,  but  not  I,  II,  or  III. 

117.  Artiads  and  Perissads.  —  Atoms  (or 

radicals)*  which  have  an  even  number  of  free 

bonds,  that  is,  dyads,  tetrads,  and  hexads,  are 

'called  Artiads.    Those  which  have  an  uneven 

number  of  free  bonds,  that  is,  monads,  triads, 
pentads,  and  heptads,  are  called  Perissads. 

118.  Theory  of  Variation  in  Quantivalence. — The 

hypothesis  is  that  an  atom  has  but  one  equivalence, 
namely  the  highest  it  ever  exhibits.  If  now  two  of  its 
bonds  mutually  saturate  one  another,  the  quantity  of 
combining  power  which  the  atom  now  has  is  less  by  two 
than  its  highest  combining  power;  if  two  pairs  of  bonds 
mutually  saturate  each  other,  the  atom  has  an  equivalence 
now  less  by  four  than  its  highest,  and  so  on.  A  heptad  may 
thus  become  pentad,  triad,  and  monad;  a  hexad  may 
become  tetrad  and  dyad. 

Compound  Molecules. 

1 19.  Relation  of  Molecular  Weight  to  density  of  com- 
pound gases. — All  molecules  have  the  same  size  (Avoga- 

*For  radicals  see  section  120 


CHEMICAL    PHILOSOPHY.  47 

dro's  law)  therefore  every  molecular  formula  not  only 
expresses  the  weight  of  the  molecule,  but  also  the  vol- 
ume it  occupies.  The  volume  occupied  by  the  atom  of 
hydrogen  is  assumed  to  be  unity;  the  volume  of  its  mole- 
cule will  therefore  be  two,  and  of  all  molecules  of  all 
bodies,  two  also.  Molecular  weight,  then,  represents  the 
weight  oi  two  volumes;  density  represents  the  weight  of 
o?te. 

Therefore  f/ie  density  of  any  homogeneous 
substance  in  the  state  of  gas  is  one-half  its  mole- 
cular weight.  Conversely,  given  the  density 
of  a  substance  in  the  state  of  gas  and  its  niole- 
cnlar  weight  is  always  equal  to  twice  the  den- 
sity. 

1 20.  Law  of  definite  and  multiple  propor- 
tions.— A  given  compound  always  contains 
the  same  elements  in  the  same  proportions. 
Thus,  a  molecule  of  water  is  always  composed 
of  hydrogen  atoms  and  oxygen  atoms,  and  al- 
w^ays  of  just  so  much  hydrogen,  two  atoms, 
and  of  so  much  oxygen,  one  atom.  Moreover, 
when  two  elements  are  capable  of  uniting  in 
different  proportions,  the  quantities  of  one 
which  unite  with  a  given  quantity  of  another 
usually  bear  a  simple  relation  to  one  another. 

121.  Differences  between  Molecules. — Molecules  are 

oi  two  classes,  e/e7Jientary*  (composed  of  like  atoms)  and 
cofnpou?id  {composed  of  unlike  atoms). 

122.  Formulse. — Compound  molecules  are  represented 

by  the    symbols  of   the    different  elements   forming  the 

♦Elementary  molecules  have  already  been  considered. 


48  DENTAL   CHEMISTRY. 

compound.  This  representation  is  termed  a  formula; 
thus,  KCl  is  a  formula  representing  one  atom  of  potassium 
and  one  atom  of  chlorine,  the  two  together  combining  to 
form  a  compound  molecule.f 

123.  Compound  Molecules,  (a)  Binaries. — Com- 
pound molecules  are  of  two  kinds:   i,  Binary;  2,  Ternary.^ 

Binary  Compounds  are  those  whose  mole- 
cule is  composed  of  two  atoms  each  one  of  a 
different  element,  as  KCl. 

Definition  6.  A  Binary  Compound  is  one 
formed  by  the  direct  union  of  two  differ- 
ent elements  or  radicals,  one  of  which  must 
he  positive  to  the  other. 

Rules.  To  name  Binaries,  put  the  name 
of  the  positive  element  first  and  the  name  of 
the  negative  element  second.  Tlien  change 
the  termination  of  tlie  negative  element  to 
-ide. 

A  compound  of  sulphur  and  potassium  is 
named  as  follows: 

(i).  Consult  Table  i,  and  find  which  is 
positive  to  the  other. 

(2).  Put  the  name  of  the  positive  element 
first,  that  of  the  neg^ative  second:  thus,  potas- 
sium sulphur. 

(3).  Change  the  termination  of  the  negative 
one,  sulphur,  to  -ide,  and  we  have  potassium 
sulphide. 

Example  i.  Name  compounds  of  the  following:  sil- 
ver and  chlorine,  sodium  and  sulphur,  iodine  and  potassi- 

tThe  entire  number  of  bonds  in  a  molecule  must  be  even. 


CHEMICAL    PHILOSOPHY.  ^g 

um,  hydrogen  and  oxygen,  hydrogen  and  arsenic,  phos- 
phorus and  zinc.  Answers:  silver  chloride,  sodium 
sulphide,  potassium  iodide,  hydrogen  oxide,  hydrogen 
arsenide,  zinc  phosphide. 

124.  Meaning  of  the  terminations  -ie,-ous, 
and  liypo-ous. — When  the  positive  of  two  ele- 
ments forming  a  compound  is  one  of  those 
which  varies  in  equivalence  (see  Table  3)  this 
variation  is  indicated  by  the  use  of  the  termi- 
nation -ic,  -ous,  and  liypo-ous. 

Rule  6.  To  name  a  binary  compound 
wliose  positive  element  is  one  wliicli  varies 
in  equivalence,  write  the  names  of  the  ele- 
ments precisely  as  in  rule  5,  but  change  the 
termination  of  the  positive  element  to  -ic,  if 
this  element  exerts  its  highest  equivalence 
(Table  3),  to  -ous  if  its  next  highest,  and 
to  hypo-oiis  if  its  lowest. 

A  compound  of  tetrad  tin  and  chlorine  would  be  called 
stann?V  chloride;  of  dyad  tin  and  chlorine,  stann<7/«  chlo- 
ride; of  monad  chlorine  and  oxygen,  JiypocYiXoxoiis  oxide. 
(Notice  in  Table  i  that  oxygen  is  negative  to  chlorine). 

Example  2.  What  do  triad  chlorine  and  oxygen  form? 
pentad  antimony  and  chlorine? 

Answers:  Chlorous  oxide.     Antlmonic  chloride. 

Rule  7.  To  write  the  formula  for  a  binary 
compound,  write  the  symbol  of  the  positive 
element  first,  then  the  symbol  of  the  negative 
element.  At  upper  right  hand  of  symbol  of 
positive  element  write  the  equivalence  of  that 
element;  do  the  same  to  the  negative.  Transfer 
the  Roman  numerals  indicating  equivalence  of 


50  DENTAL   CHEMISTRY. 

positive  element  to  lower  right  hand  of  neg'a- 
tive  element.  Transfer  the  Roman  numerals 
indicating-  equivalence  of  the  negative  element 
to  the  lower  right  hand  of  positive  element. 
Write  all  transferred  numerals  in  Arabic  fig- 
ures,  changing  them  from  Roman.* 

To  write  the  formula  for  stannic  chloride: 

(i)     Symbol  of  positive  element,  Sn; 

(2)  Symbol  of  negative  element,  CI; 

(3)  Arranged  in  order,  SnCl; 

IV    I 

(4)  Equivalence  indicated,  SnCl; 

(5)  Numerals  transferred,  SnCl* 

N.  B. — It  is  really  never  necessary  to  write  the  figure 
I,  as  the  symbol  itself  indicates  one  atom. 

If  several  molecules  of  the  binary  compound  are 
to  be  denoted,  write  the  formula,  inclose  in  brackets,  and 
write  the  multiplier  as  a  small-sized  figure  at  lower  right 
hand,  or  write  a  full-sized  figure  before  the  formula  not 
inclosed  in  brackets. 

Suppose  it  be  required  to  denote  3  molecules  of  sodium 
iodide:  the  formula  is  Nal  which  denotes  one  moleaile  with 
all  the  properties  of  that  molecule,  namely,  a  certain  un- 
changeable weight — the  sum  of  the  weights  of  the  two 
atoms,  called    the  molecular  weight — or,  in  the   case  of 


♦Rule  7  has  been  deduced  from  the  following:  in  all  cases  of 
chemical  combination  the  chemical  affinity  of  each  atom  must  be 
satisfied.  Atoms  of  the  same  valence,  then,  may  mutually  saturate  one 
another,  and  unite  in  the  ratio  of  one  to  one.  Atoms  of  different  val- 
ence cannot  unite  in  the  ratio  of  one  to  one;  each  one  must  furnish  the 
same  number  of  bonds,  which  number  is  in  all  cases  the  least  com- 
mon multiple  of  the  two  valences.  Divide  this  1.  c.  m.  by  each  val- 
ence to  obtain  the  number  of  atoms  of  each  constituent  in  the  com- 
pound. Thus,  triad  nitrogen  and  dyad  oxygen:  6-^-3  shows  the 
number  of  nitrogen  atoms;  6-f-2=  the  number  of  oxygen  atoms. 


CHEMICAL    PHILOSOPHY. 


51 


gases,  a  certain  volume  always  the  same;  to  denote  3 
molecules,  write  the  figure  3  before  the  formula:  thus, 
3NaI;  or  bracket  the  formula  (Nal)  and  write  the  figure  3 
in  small-sized  type  at  the  lower  right  hand:  thus  (Nal)3. 

Example  3.  Denote  five  molecules  of  magnesium  ox- 
ide, six  of  silver  chloride,  three  of  chlorous  oxide. 

Answers:  sMgO  or  (MgO)5,  6AgCl  or  (AgCOe,  3CI2O3 
or  (01203)3. 

Remark:  In  order  to  apply  Rule  7  successfully,  the 
following  must  be  borne  in  mind:  if  a  formula,  obtained 
by  Rule  7,  shows  after  each  symbol  figures  which  contain 
common  factors,  these  common  factors  must  be  removed 
from  the  figures;  thus,  the  formula  for  stannic  oxide,  ac- 
cording to  Rule  7,  is  SngO^;  but  2  and  4  contain  the 
common  factor  2,  therefore  divide  each  by  2  and  the  re- 
sult, Sn02,  is  the  proper  formula.  * 

Example  4.  Write  the  formulae  for  platinic  sulphide, 
hyposulphurous  oxide,  stannous  sulphide: 

Answers.  PtSj,  SO,  SnS. 

125.  Yariation  in  Equivalence  of  Certain  Elements. — 
Certain  elements  vary  in  equivalence  in  a  puzzling  man- 
ner, e.  g.  mercury,  copper,  iron,  aluminium.  As  com- 
pounds of  these  metals  are  important,  it  is  desirable  that 
the  variations  in  equivalence  be  thoroughly   understood. 

Mercury  is  a  dyad;  in  some  compounds,  however,  we 
find  two  atoms  of  mercury  and  two  of  a  monad,  as  for  ex- 
ample in  calomel,  the  formula  for  which  is  Hgg  CI2.  The 
formula  Hg2Cl2  is  explained  graphically:       Hg — CI. 

I 
Hg-Cl. 
Two  atoms  of  dyad   mercury  would    have  four  bonds 
(Rule  4,  N.  B.),  and  ought  to  take   four  atoms  of  monad 
chlorine,    but    two     of    the  bonds   of  the    mercury  satisfy 

*Sn204  is  the  same  as  2Sn02  or  (SnOs)  2 ,  that  is  two  molecules  of  Sn 

Oo. 


52  DENTAL   CHEMISTRY 

eac/i  ot/ier  instead  oi  requiring  two  bonds  of  chlorine;  the 
other  two  bonds  of  the  mercury  are  satisfied  by  means  of 
two  chlorine  bonds,  hence  Hgj  Clj,  and  not  CI*  as  might 
be  expected.  The  same  may  be  said  of  copper.  Such 
compounds  are  called  mercurous  or  cuprous  compounds. 
Variation  in  equivalence  may,  in  general,  be  explained  by 
graphic  formulae. 

Rule   8.    To   write   formulae   containing 

mercury  or  copper,  assign  to  mercuric  atoms 
and  cit^pric  atoms  an  equivalence  of  two  as  in 
table  4;  to  7ner citrous  and  cuprous  assign  an 
equivalence  of  one.  N.  B.  In  the  case  of  mer- 
curous and  cuprous  note  that  two  atoms  of 
mercury  or  copper  require  two  only  of  a  unival- 
ent element. 

Example  5.  Write  the  formulae  for  mercuric  chloride, 
mercurous  iodide,  cupric  oxide,  mercurous  chloride. 

Answers.     HgClg,  Hgl  or  HgJ.,  CuO,  HgCl  or  HgaCl?. 

Compounds  of  iron  are  known  to  exist  in  which  the 
molecule  may  consist  of  two  atoms  of  iron  and  six  of  a 
monad,  as  for  example,  ferric  chloride,  FcaCle;  to  such 
compounds  the  \.exm.  ferric  is  applied. 

Rule  Q.      To   write   formulje   containing 

iro7i,^ivQ  two  atoms  of  iron  together,  an  equiva- 
lence of  six,  if  the  compound  is  called  ferric. 
In  ferrous  compounds  assign  equivalence  of 
two  to  iron. 

N.  B.  While  HggClz  is  often  written  in  the  simpler  form 
HgCl,  it  is  not  customary  to  write  FeoClg  in  any  simpler 
fashion;  the  formulae  of  other  compounds  are  usually  sim- 
plified. 

Example  6.  Write  the  formulae  for  ferric  chloride,  fer- 
ric oxide,  ferrous  sulphide,  ferrous  oxide,  aluminic  chloride. 


CHEMICAL    PHILOSOPHY. 


Answers.  FegCle,  FegOs,  [that  is  (Fe2)20«],  FeS,  FeO, 
A^Cls — like  ferric. 

Rule  10.  To  read  Binary  Formulje,  ob- 
serve from  figure  at  lower  right  hand  of  nega- 
tive element  what  the  equivalence  of  the  posi- 
tive element  is.  If  the  positive  element  is  in 
its  highest  equivalence  (Table  3)  change  its 
termination  to-ic  etc.,  as  in  Rule  6.  Note  that 
where  sulphur  is  the  positive  element  and  the 
negative  element  oxygen,  the  figure  3  at  the 
lower  right  hand  of  oxygen  will  denote  sul- 
phur as  a  hexad,  hence  sulphur/^::  e.  g.,  SaOs 
or  SO3  is  sulphur/<;  oxide. 

In  reading  binary  formulae,  the  termination  of  the  nega- 
tive element  is  always  changed  to  -ide. 

Example  7.  Read  the  formulae  of  the  following  com- 
pounds used  in  dental  medicine: 

I,  KBr.     2,  KI.     3,  HCl.     4,  SnCU.     5,  KCl.     6,  K^O. 

7,  HoO.  8,  Al.Cle.  9,  AS-.O3.  10  AuCls.  II.  HgCl^. 
12,  HgCl.  13,  Hgl.  14,  Znl^.  15,  ZnO.  i5,  MgO.  17, 
CaO. 

Answers,  i,  potassium  bromide.  2.  potassium  iodide, 
3,  hydrogen  chloride.  4,  stannous  chloride.  5,  potas- 
sium chloride.     6,  potassium  oxide.     7,  hydrogen  oxide. 

8,  aluminic  chloride.  9,  arsenous  oxide.  10.  auric  chlo- 
ride. II,  mercuric  chloride.  12,  mercurous  chloride  (see 
Rule  8).  13,  mercurous  iodide.  14,  zinc  iodide.  15, 
zinc  oxide.     16,  magnesium  oxide.     17,  calcium  oxide. 

Example  8.  Read  the  following  formulae  (of  use  in 
studying  ternaries):  CIA,  N.Oj,  SO3,  SO,  Cl^O.  CUO3, 
CO2. 

Answers.     Chloric  oxide,  nitric  oxide,  sulphuric  oxide, 


54 


DENTAL   CHEMISTRY. 


hyposulphurous    oxide,    hypochlorous    oxide,     chlorous 
oxide,  carbonic  oxide. 

126.  Radicals. — A  radical  is  an  unsaturated 
group  of  atoms.  It  possesses  free  bonds, 
hence  may  enter  into  combination  like  single 
atoms. 

Example:  HO  is  an  unsaturated  group  of  atoms,  for 
one  bond  of  the  oxygen  is  unprovided  for,  thus,  H — O — . 
Hence  HO  is  a  radical. 

127.  Nomenclature,  and  equivalence  of  radicals.-The 

names  of   compound   radicals    end    in   -yl.     Thus,  HO    is 
called  hydroxyl. 

The  equivalence  of  compound  radicals  is  al- 
ways equal  to  the  number  of  unsatisfied  bonds, 
that  is  to  the  difference  resulting-  from  the  sub- 
traction of  the  equivalence  of  one  of  its  con- 
stituents from  that  of  the  other: 

Thus  the  equivalence  of  HO  is  one  because  it  has  one 
unsatisfied  bond,  that  is,  2  (equivalence  of  oxygen)  minus 
I  (equivalence  of  hydrogen)  equals  i  (equivalence  of 
hydroxyl). 

Radicals  are  therefore  perissad  and  artiad  like  atoms. 
Perissad  radicals  can  not  exist  free  except  by  combining 
with  one  another. 

128.    Ternary  Compounds. — 

Definition  7.  A  ternary  compound  is  one 
whose  molecule  is  composed  of  three  or  more 
different  kinds  of  atoms:  thus,  KCIO3  is  a  ter- 
nary because  composed  of  K,  CI,  and  O.  In 
every  ternary  formula  there  are  at  least  three 
different  symbols. 

In  ternaries  the    dissimilar   atoms  are  linked   together 


CHEMICAL   PHILOSOPHY, 


■Oi) 


by  a  third  atom,  and  ternaries  are  of  two  classes,  (a) 
those  whose  dissimilar  atoms  are  linked  by  a  bivalent 
atom,  and  (d)  those  whose  dissimilar  atoms  are  linked  by 
a  trivalent  atom.  The  first  class  comprises  many  inor- 
ganic compounds,  the  second  many  organic. 

In  the  first  class  the  linking  is  usually  performed  by 
oxygen,  sometimes  by  sulphur,  sometimes  by  selenium 
and  tellurium. 

129.  Ternaries  of  the  first  class.  Dissim- 
ilar atoms  linked  by  oxygen  or  sulphur. 

There  are  three  kinds:  acids,  bases,  and 
salts. 

Definition  8.  Acids  are  corrosive  substances 
having:  usually  a  sour  taste,  neutralizing  alka- 
lies, and  changing-  blue  vegetable  colors  to 
red.  They  give  off  hydrogen  when  brought 
into  contact  with  a  metal.  Acids  are  either 
(hydracids),  ox-acids,  or  sulpho-acids.  [Hy- 
dracids  are  binary  compounds  of  hydrogen, 
and  are  hydrochloric,  HCl;  hydrobromic, 
HBr;  hydriodic,  HI;  hydrosulphuric,  H2S. 
They  are  also  called  hydrogen  (or  hydric) 
chloride,  hydrogen  or  hydric  bromide,  etc.]. 

Ox-acids  are  composed  of  hydrogen,  some 
negative  element,  and  oxygen:  as  HNO3, 
nitric  acid. 

Sulpho-acids  are  composed  of  hydrogen, 
some  negative  element,  and  sulphur,  as  H2CS3, 
sulpho-carbonic  acid. 


5(3  DENTAL   CHEMISTRY. 

Rule  II.  To  write  the  formulae  of  many 
ox-acids  and  sulplio-acids:* 

1.  Write  the  formula  of  corresponding  ox- 
ide or  sulphide,  simplifying"  if  possible. 

2.  Add  formula  for  a  molecule  of  water, 
HjO,  in  case  of  an  ox-acid,  or  H2S  in  case  of 
a  sulpho-acid. 

3.  Simplify  if  possible. 

Suppose  the  formula  for  nitric  acid  be  re- 
quired: first  write  the  formula  for  the  corre- 
sponding oxide.  By  this  we  mean  nitricf 
oxide  and  not  nitrous  or  hyponitrous.  For- 
mula for  nitric  oxide  is  N2O5;  add  H2O  and  we 
have  H2N2O6 — the  only  thing  to  be  added 
arithmetically  being  O  to  O5  making  Oe.  Now 
simplify  by  taking  out  the  common  factor  2 
and  we  have  HNO3.  (See  also  Table  4  and 
note  Rule  14,  page  60). 

♦Rule  11  is  deduced  from  the  following:  1.  An  acid  molecule  is 
one  consisting  of  one  or  more  negative  atoms  united  by  oxygen  to 
hydrogen. 

2.  Ternaries  are  formed  by  the  direct  union  of  the  oxide  of  a 
more  positive  atom  with  the  oxide  of  a  less  positive  or  negative 
atom.  Whenever  water  is  the  positive  oxide,  the  body  produced  is 
an  acid:  thus,  of  the  two  oxides,  sulphuric  and  hydric,  sulphuric 
oxide  is  the  negative  and  hydric  oxide  (water)  the  positive,  there- 
fore the  two  on  combining  form  an  acid. 

3.  An  acid,  then,  may  be  formed  by  the  combination  of  a  nega- 
tive oxide  with  water. 

Acids  are  also  formed  from  water,  H — O — H,  by  exchanging  an 
atom  of  H  for  a  negative  monad.  Thus,  hypochlorous  acid:  ex- 
change one  atom  of  H  for  Cl  and  there  is  formed  Cl — O— H. 

fThis  rule  gives  always  hydrated  acids  and  is  of  service  in  obtain- 
ing formulae  of  salts.     The  use  of  Table  4  is  to  be  preferred. 


CHEMICAL    PHILOSOPHY.  5'J' 

Note.  The  formulae  for  phosphoric,  boric,  arsenic, 
arsenous,  and  hypophosphorous  acids  are  obtained  by- 
adding  more  than  one  molecule  of  water  or  (better)  by 
Table  4,  page  60. 

Example  9.  Write  the  formulae  for  the  following  acids: 
sulpho-carbonic,  sulphuric,  sulphurous,  hypochlorous,  ni- 
trous. 

Answers:     H2CS3,  H^SO,,  H2SO3,  HCIO,  HNO^. 

N.  B.  The  oxygen  or  sulphur  of  acids  is  said  to  have 
a  linking  function,  uniting  the  hydrogen  to  the  rest  of  the 
molecule;  thus,  the  formula  for  nitric  acid  may  be  repre- 
sented graphically  as  follows: 

H — O — N=0  j  the  hydrogen  atom  being  linked  to  the 
^O  I  rest  of  the  molecule  by  the  oxygen  atom. 

Definition  9.  Bases  are  the  opposite  of 
acids.  They  neutrahze  acids,  either  partly  or 
entirely,  restore  blue  colors  to  vegetable  colors 
turned  red  by  acids,  when  concentrated  decom- 
pose fats,  forming"  soap,  and  act  on  the  tissues 
as  caustics. 

Acids  unite  with  metals  to  form  salts,  bases 
with  acids  to  form  salts,  hydrogen  being 
evolved  in  the  one  case,  water  formed  in  the 
other. 

Inorganic  bases  are  termed  hydrates,  by 
which  term  we  shall  hereafter  call  them.  The 
molecule  of  a  hydrate  is  composed  of  a  posi- 
tive atom  or  atoms,  hydrogen,  and  oxygen: 
thus,  R  O  H.  R  denoting  any  number  of 
positive  atoms. 

The  oxygen  of  bases  is  said  to  link  the  hy- 
drogen to  the  positive  element. 


58  DENTAL   CHEMISTRY. 

The  formula  for  sodium  hydrate  may  be  represented 
graphically  as  follows:  Na — O — H,  in  which  the  positive 
atom  is  linked  by  the  atom  of  oxygen  to  the  hydrogen. 

Rule  12.  To  write  the  formula  for  a  hy- 
drate, first  write  the  symbol  of  the  positive 
element  with  its  equivalence  over  it,  then  write 
OH  in  brackets  with  an  equivalence  of  i  over 
it.  Next  exchange  fig^ures  representing-  equiva- 
lences, as  in  binaries.*'* 

To  write  the  formula  for  calcium  hydrate: 

1.  Ca". 

2.  (OH)^ 

3.  Ca"(OH)^ 

4.  Ca(OH)2.     Calcium  hydrate. 

Calcium  hydrate  represented    graphically    would     be 
P    /OH 
'-^\OH. 

Example  10.  Write  the  formulas  for  barium  hydrate, 
mercuric  hydrate,  arsenous  hydrate,  cuprous  hydrate. 

Answers.     Ba(OH)2,  Hg  (OH)^,  As(OH)3,  CuOH. 

N.  B.  Where  one  molecule  only  of  OH  occurs  it  is 
not  necessary  to  bracket.  Instead  of  OH  some  authors 
write  HO. 

Definition  10.     A  salt  resembles  neither  an 


*Rule  12  is  deduced  from  the  following:  a  molecule  of  water  con- 
sists of  two  atoms  of  hydrogen  linked  by  oxygen.  Exchange  one  of 
these  hydrogen  atoms  for  a  positive  univalent  atom,  and  a  base  re- 
sults. Thus,  water  is  H — O — H:  exchange  H  for  K  and  we  have 
K — O — H.  But  when  it  is  necessary  to  form  the  hydrate  of  a  bival- 
ent atom  it  is  necessar>'  to  take  two  molecules  of  water  and  one  of 
the  bivalent  element.  Thus,  if  calcium  hydrate  be  required,  take  2 
H2O,  or  H4O2.  Substitute  Ca  for  H2  and  we  have  CaHaOs  or  Ca(H0)2, 
The  formulae  of  bases  may  be  obtained  also  by  direct  union  of  water 
with  a  positive  oxide. 


CHEMICAL   PHILOSOPHY.  59 

acid  nor  a  base;  its  molecule  consists  of  a  pos- 
itive atom  united  by  oxygen  to  a  negative 
atom ;  thus,  KNOsi  K  positive  atom,  N  nega- 
tive, O  oxygen. 

Exceptions.  A  salt  may  be  formed  from  an  acid  and  a 
metal,  the  latter  replacing  all  the  hydrogen  of  the  acid; 
acids  whose  molecule  contains  two  atoms  of  hydrogen  may 
not  always  exchange  both  atoms  for  atoms  of  a  metal,  but 
one  may  be  replaced  and  the  other  not:  thus,  NaHSO^. 
Such  a  salt  is  called  an  acid  salt.  Those  described  in  Defi- 
nition 10  are  called  normal  salts.  Double  salts  are  those 
whose  molecules  consist  of  two,  different,  positive  atoms 
united  by  oxygen  to  the  negative  atom:  thus,  KNaSO^, 
called  potassium  sodium  sulphate,  or  the  double  sulphate 
of  potassium  and  sodium. 

Rule  13.*    To  write  the  formula  of  a  salt.— 

First  write  the  formula  of  the  acid  which, 
with  the  metal,  forms  the  salt;  bracket  the 
non-hydrogen  part  of  the  acid  formula,  erase 
the  H,  and  put  in  its  place  the  symbol  of  the 
metal;  write  the  equivalence  of  the  metal  after 
the  bracket,  and  simplify  if  possible. 

Note  that  -ate  in  a  salt  corresponds  to  -ic  in  an  acid, 
-ite  to  -ous,  hypo-ite  to  hypo-ous. 

Examples:  sodium  sulph^/^  is  formed  from  sulphurzV 
acid,  sodium  sulphite  from  sulphur(?z«  acid,  sodium  hypo- 
chlorite from  hypochlorw«  acid. 

Suppose  the  formula  for  mercuric  nitrate  be  required. 
The  termination  -ate  in  a  salt  is  used  by  chemists  to  sig- 

*In  writing  the  formulse  of  a  salt,  as  many  molecules  of  the 
acid  must  be  taken  as  is  necessary  to  furnish  a  number  of  hydro- 
gen atoms  equal  to  the  L.  C.  M.  of  the  number  of  hydrogen  atoms  in 
the  acid  [basicity]  and  the  valence  of  the  replacing  atom. 


go  DENTAL    CHEMISTRY. 

nify  a  higher  equivalence  of  the  negative  element,  just  as 
-ic  is  used  in  the  case  of  acids: 

1.  Write  the  formula  for  nitric  acid:  HNO3. 

2.  Bracket  the  non-hydrogen  part:  H(N03). 

3.  Erase  the  H  and  put  into  its  place  the  symbol  of 
the  metal  mercury:  HgNOs. 

4.  Write  the  equivalence  of  metal  after  bracket:  Hg 
(NOaV 

5.  Simplify.  (Not  possible  in  this  case). 

The  formulae  of  salts  may  be  written  much  more  rapidly 
if  the  following  table  of  compound  negative  radicals  be 
committed  to  memory, 

TABLE  4. 

MONADS.  DYADS. 

NO3  (Nitrates).  SO*  (Sulphates). 

NO2  (Nitrites).  SO3  (Sulphites). 

CIO3  (Chlorates).  CO3  (Carbonates). 

PH2O2  (Hypophosphites).  CrO*  (Chromates). 
CIO  (Hypochlorites).       CrjO?  (Bichromates). 

TRIADS.  TETRADS. 

PO4  (Phosphates).  FeCye*  (Ferrocyanides). 

ASO4  (Arsenates).  SiO*  (Silicates). 

AsOa  (Arsenites).  P2O7  (Pyrophosphates). 
BO3  (Borates). 

HEXADS. 

FcaCyia*  (Ferricyanides) 
Rule  14,     To  write  tlie  formula  of  a  salt 
Iby  use  of  Table  4.    First  write  the  symbol 


*These  will  be  explained   under   the   head   of  theory   of  organic 
chemistry. 


CHEMICAL   PHILOSOPHY.  gl 

for  the  metal,  with  its  equivalence  indicated 
over  it;  next  write  the  formula  for  the  com- 
pound radical  with  its  own  equivalence  over 
it;  exchange  equivalences;  simplify  if  pos- 
sible. 

Suppose  the  formula  of  zinc  hypophosphite  be  re- 
quired: 

I.   Zn"{?n,o,y. 

N.  B.  Acids  being  regarded  by  some  as  salts  of  hydro- 
gen, their  formulae  may  be  written  from  Table  4:  thus, 
sulphuric  acid  may  be  written  as  hydrogen  sulphate: 

1.  H'(SO,)", 

2.  H^SOi. 

Phosphoric  acid  and  boric  acid  should  be  written  from 
Table  4  altogether,  as  they  are  meta-  and  ortho-acids  re- 
spectively, as  regards  their  salts  used  in  dental  medi- 
cine.* 

Example  11.  Write  the  formulae  for  the  following  salts 
used  in  dental  medicine:  cadmium  sulphate,  cupric  sul- 
phate, zinc  sulphate,  magnesium  sulphate,  magnesium 
hypochlorite,  calcium  sulphite,  calcium  hypophosphite 
(by  Table  4),  calcium  carbonate,  silver  nitrate. 

Answers:  CdSO,,  CuSO,,  ZnSO,.  MgSO,,  Mg(C10)2, 
CaSOs,  Ca(PHA)2,  CaCOs,  AgNOj. 


*An  ortho-acid  is  one  whose  molecule  contains  as  much  H  as  O: 
thus,  ortho-phosphoric  acidis  H5PO5  .  The  term  "ortho-phosphoric" 
acid  is,  however,  often  given  to  H3PO4 ,  which  is  really  di-meta-phos- 
phoric  acid.  A  meta-acid  is  derived  from  an  ortho-acid  by  subtrac- 
tion of  one  or  more  molecules  of  water  from  the  formula  of  the  ortho- 
acid. 


62 


DENTAL   CHEMISTRY 


Example  12.7 
following: 

1.  Cupric  ferrocyanide,     9. 

2.  Barium  chromate,        10. 

3.  Lead  sulphate,  11. 

4.  Ferric  sulphate,  12. 

5.  Ferric  hypophosphite, 

6.  Aluminic  hydrate, 

7.  Ferrous  sulphate,         13. 

8.  Sodium  hypophosphite, 
Answers: — 

1.  CuaFeCye, 

2.  BaCrOi, 

3.  PbSOt, 

4.  Fe,(SO03, 

5.  Fe2(PH,0,)^ 

6.  AMHOje, 

7.  FeSOi, 


For  practice   write  the  formulae  of  the 


Potassium  hypochlorite. 
Calcium  hypochlorite, 
Potassium  sodium  sulphate, 
Potassium  sodium  acid 
phosphate,  or  potassium  so- 
dium hydrogen  phosphate. 
Sodium  hydrogen  carbon- 
ate or  sodium  bicarbonate. 


9- 
10. 
II. 
12. 
13- 


Na(PH,0,). 

KCIO, 

Ca(C10\, 

KNaSO,, 

KNaHPO,. 

NaHCO,. 


TERNARIES    OF   THE  SECOND  CLASS.      DISSIM- 
ILAR ATOMS  LINKED  BY  TRIADS. 

130.  Ternaries  of  the  second  class  are  linked 
mostly  by  nitrog"en.  There  are  three  kinds  of 
those  linked  by  nitrogen  :-<^;;//^^5,in  whose  mole- 
cule negative  atoms  are  linked  to  hydrogen  by 
nitrogen, — amines,  in  whose  molecule  ^positive 
atoms  are  linked  by  nitrogen  to  hydrogen,  and 
alkalaniides,  in  whose  molecule  positive  atoms 
are  linked  by  nitrogen  to  negative  ones.  All 
may  be  derived  by  substitution  from  ammo- 
nia. 


■fThis  example  may,  at  the  discretion  of  the  teacher,  be  omitted. 


CHEMICAL   PHILOSOPHY. 


63 


Rule  15.  To  read  formulas:  commit  to  mem- 
ory the  following  table: 

TABLE  5. — USUAL    TERMINATIONS  IN  VARIOUS 

BINARY  AND  TERNARY   FORMULA  * 

BINARIES. 

Hydrochloric  acid  and  all  chlorides  end  in 
CL.f 

Hydrobromic  acid  and  all  bromides  end 
in  Br„. 

Hydriodic  acid  and  all  iodides  end  in  !„. 

Hydrosulphuric  acid  and  all  sulphides  end 
in  Sn. 

Hydrofluoric  acid  and  all  fluorides  end  in 
F„  or  FL. 

All  oxides  end  in  On. 

TERNARIES. 

All  hydrates  end  in  (OH)n. 

Sulphuric  acid  and  all   sulphates  end  in 

(SOOn. 

Phosphoric  acid  and  all  phosphates  end  in 

(PO.x. 

Chromic  acid  and  all  chromates  end  in 
(CrOOn. 

Boric  acid  and  all   borates  end  in  (BOsX. 

Nitric  acid  and  all  nitrates  end  in  (N03)„. 

Chloric  acid  and  all  chlorates  end  in 
(CIO3X. 

Sulphurous  acid  and  all  sulphites  end  in 
(SOQa. _^ 

♦Graphic  formulas  are  not  included  in  this  table, 
■fn  denoting  any  number. 


g4  DENTAL   CHEMISTRY. 

Hypochlorous  acid  and  all  hypochlorites 
end  in  (C10)„. 

Hypophosphorous  acid  and  all  hypophos- 
phites  end  in  (PH202)„. 

Suppose  now  that  the  formula  to  be  read  be  HNO3:  it 
begins  with  H  and  contains  no  positive  element,  there- 
fore is  an  acid;  it  ends  in  NO3,  therefore  by  Table  5  is  ni- 
tnV  acid.  Suppose  it  be  required  to  read  the  formula 
Al2(OH)6;  it  is  not  an  acid  because  it  does  not  begin  with 
H,  but  is  a  hydrate,  because  it  ends  in  OH;  and  it  is  alum- 
inic  hydrate  by  Rule  9.  Suppose  the  formula  be  K2CO3. 
It  is  not  an  acid,  nor  a  hydrate,  but  is  a  salt,  because  end- 
ing in  oxygen  preceded  by  a  negative  element.  It  is  a 
carbonate  by  Table  5,  hence  is  potassium  carbonate. 
Suppose  the  formula  be  Fe2(Cr04)3;  it  is  a  salt,  and  by 
Table  5  a  chromate,  and  by  Rule  g,  ferric  chromate. 

Example  13.  Read  the  formulae  given  in  the  answers 
to  example  12. 

N.  B.  Consideration  of  formulae  of  organic  compounds 
is  deferred  to  Chap.  IV,  but,  as  a  sharp  line  of  demarca- 
tion cannot  always  be  drawn  between  many  inorganic  and 
organic  compounds,  the  beginner  will  do  well  to  note  the 
following: 

TABLE  6 — ORGANIC   COMPOUNDS. 
BINARIES. 

Hydrocyanic  acid  and  all  cyanides  end  in 
(CN)„. 

Hydroferrocyanic  acid  and  all  ferrocyan- 
ides  end  in  (FeCy6)„. 

Hydroferricyanic  acid  and  all  ferricyanides 
end  in  (Fe2Cyi2)„. 

Sulphocyanic  acid  and  all  sulphocyanates 
end  in  (CNS)„. 


CHEMICAL   PHILOSOPHY.  65 

TERNARIES. 

Acetic    acid    and    all    acetates    end   in 

(QHaOOn. 

Oxalic  acid  and  all  oxalates  end  in  (CaOOn. 
Tartaric    acid    and  all  tartrates   end    in 

(QHA)„. 

Salicylic    acid  and  all   salicylates  end  in 

(GHA)„. 

Example  14.*  Read  the  following  formulae:  iPb(C2H3 
'02)2,  K2CA.  KCN,  K,Fe(CN)6  or  Cye,  KNaQHA. 
Na(CN)S  or  CyS,  Na^QH^Os. 

Answers.  Plumbic  acetate,  potassium  oxalate,  potassi- 
um cyanide,  potassium  ferrocyanide,  potassium  sodium 
tartrate,  sodium  sulphocyanate,  sodium  salicylate. 

N.  B.  (a)  Ammonium  Compounds  begin  with  (NH4),  a 
univalent  positive  radical:  ammonium  chloride  is,  there- 
fore, (N  H4)C1,  ammonium  sulphate  (NH4)8S04,  etc.,  etc. 

Example  15.  Read  the  following:  NH4NO3,  NH^HO, 
NH.MgPO^. 

Answers.  Ammonium  nitrate,  ammonium  hydrate,  am- 
monium-magnesium phosphate. 

(d)  Nomenclature  —  Old  and  New. — The  prefixes 
proto-  a.nd  per-  are  used  in  older  works  instead  of  -ic  and 
-afe  on  the  one  hand  and  -ous  and  -ite  on  the  other;  for 
example,  instead  of  mercuroiis  iodide,  older  writers  speak 
oi  t\\.Q  protiodide  oi  mercury ;  \nsX&2i<\  of  fernc  sidphate  the 
persidphate  of  iron  is  the  name  given. 

The  term  acid  in  some  of  the  older  books  is  given  to 
what  is  now  called  anliydride  or  negative  oxide;  thus  ar- 
senoiis  acid  is  used  by  some  writers  as  the  name  for  AsoOs 
which  in  this  book  is  called  arsenious  anhydride  or  arsen- 
ous  anhydride.     The  term  anhydrous  acid  is  also  used  by 

*This  example  may  be  omitted  until  organic  chemistry  be  taken  up. 


66  DENTAL    CHEMISTRY. 

some  writers  instead  of  anhydride  or  oxide,  and  the  term 
hy dr ate d  acid  for  what  in  this  book  is  called  simply  acid. 
Oxides  of  sodium,  potassium,  magnesium,  etc.,  are  called 
soda,  potassa,  magnesia,  lime,  etc.,  by  some  authors. 

Example  i6.  Give  the  new  names  for  the  following: 
baryta,  perchloride  of  tin,  protoxide  of  mercury,  perchlo- 
ride  of  iron,  potash,  alumina,  protochloride  of  mercury, 
anhydrous  phosphoric  acid. 

Answers.  Barium  oxide,  stannic  chloride,  mercurous 
oxide,  ferric  chloride^  potassium  oxide,  aluminum  oxide, 
mercurous  chloride,  phosphoric  anhydride  or  oxide. 

N.  B.  Remember  that  in  modern  text  books  the  term 
anhydride  simply  means  an  oxide  which  can  combine 
with  the  elements  of  water  to  produce  an  acid,  or  in  other 
words  an  acid  minus  water. 

In  many  new  text  books,  notably  those  by  English 
authors,  we  find  numeral  prefixes,  as  di-  tri-  pent-,  etc. 
Thus,  CSgis  called  carbon  disulphide,  PoOj  phosphorus 
pentoxide,  etc.,  etc.  The  old  term  for  di-  is  bi-  Older 
writers  use  the  prefix  sesqui-  in  compounds  where  there 
are  two  atoms  of  one  element  and  three  of  another;  they 
also  call  hydrochloric  acid  muriatic  acid,  and  term  chlo- 
rides muriates.     Sulphides  are  termed  sjdphurets  by  some. 

Example  17.  Give  new  names  for  the  following:  ses- 
quioxide  of  iron,  bisulphuret  of  carbon,  sesquisulphide  of 
iron,  muriate  of  ammonia,  bichloride  of  mercury,  proto- 
sulphuret  of  iron,  peroxide  of  hydrogen. 

Answers.  Ferric  oxide  (FegOg),  carbonic  disulphide, 
ferric  sulphide  (FegSs),  ammonium  chloride,  mercuric 
chloride,  ferrous  sulphide,  hydric  dioxide. 

Commercial  terms. — For  these,  such  as  "salts  of  tar- 
tar," "sal  volatile,"  etc.,  etc.,  see  Glossary  at  the  end  of 
the  book. 

131.  Chemical  change.— In  every  chemical 
chang-e  one  or  more  substances  cdiWtd  factors 


CHEMICAL    PHILOSOPHY.  g7 

chang-e   into   one  or  more  substances  called 
products. 

Example:  zinc  and  sulphuric  acid  change  into  zinc  sul- 
phate and  hydrogen.  Factors:  zinc  and  sulphuric  acid. 
Products:  zinc  sulphate  and  hydrogen. 

132.  Fundamental  laws  of  chemical 
change. — I.  The  sum  of  the  weights  of  the 
products  of  a  chemical  change  are  exactly 
equal  to  the  sum  of  the  weights  of  the  factors. 
(Law  of  conservation  of  mass. — Lavoisier's 
Law). 

Example:  if  phosphorus  be  burned  in  a  closed  jar,  the 
latter  will  weigh  as  much  after  the  combustion  as  before. 
That  is,  the  weight  of  the  products  of  the  combustion  is 
the  same  as  that  of  the  factors. 

IL  In  any  well-marked  chemical  change 
the  relative  weights  of  the  several  factors  and 
products  are  definite  and  invariable. 

(Law  of  Definite  Proportions  by  Weight). 

Suppose  a  given  amount  of  sal-soda  yields  with  hydro- 
chloric acid  a  given  amount  of  common  salt.  Five  times 
the  amount  of  sal-soda  will  yield  five  times  the  amount  of 

salt. 

III.  In  any  well-marked  chemical  change 
the  relative  volumes  of  the  aeriform  factors 
or  products,  if  measured  under  the  same  con- 
ditions, bear  to  each  other  a  simple  numerical 
ratio.  (Law  of  Definite  Proportions  by  Vol- 
ume— Gay-Lussac's  Law). 

Example:  oxygen  combining  with  sulphur  forms  sul- 
phurous oxide  gas:  the  volmne  of  the  sulphurous  oxide  is 
the  same  as  that  of  the  oxygen;  two  volumes  of  hydrogen 


g3  DENTAL   CHEMISTRY. 

gas  combine  with  one  of  oxygen  to  form  two  volumes  of 
vapor  of  water. 

133.  Keactions — The  chemical  action  be- 
tween two  substances  on  each  other  when 
brought  tog-ether  is  called  a  reaction.  The 
body,  which  when  added  to  another  causes 
the  change,  is  called  a  reagent. 

134.  Manner  of  Chemical  Action. — Chemical  changes 
may  take  place  as  follows: 

(a)  By  direct  union  of  simpler  molecules,  forming  a 
more  complex  one. 

(d)  By  separation  of  a  complex  molecule  into  sim- 
pler ones. 

(c)  By  substitution  in  a  molecule  of  one  atom  or  group 
of  atoms  for  another  or  for  several  others. 

(d)  By  mutual  exchange  of  atoms  between  molecules. 

(e)  By  re-arrangement  of  atoms  within  a  single  mole- 
cule, as  shown  by  conversion  of  ammonium  cyanate  into 
urea.  • 

Examples: 

1,  Chemical  change  of  the  first  kind  is  represented  by 
synthetical  reactions;  thus,  hydrogen  (one  molecule)  and 
chlorine  (one  molecule)  form  hydrochloric  acid  (two  mole- 
cules). 

2.  Chemical  change  of  the  second  kind  is  represented 
by  analytical  reactions:  thus  calcium  carbonate  (one 
molecule)  yields  one  molecule  of  calcium  oxide  and  one 
molecule  of  carbon  dioxide. 

3.  Chemical  change  of  the  third  kind  is  represented 
by  the  so-called  substitution  reactions,  as  for  example 
when  one  atom  of  potassium  replaces,  i.  e.,  is  substituted 
for,  one  atom  of  hydrogen  in  the  molecule  of  water,  form- 
ing potassium  hydrate. 

4,  Chemical  change  of  the  fourth  kind  is   represented 


CHEMICAL   PHILOSOPHY.  gQ 

by  the  so-called  metathetical  reactions,  as  when  ammoni- 
um sulphate  and  calcium  carbonate  exchange  atoms 
mutually  between  their  molecules,  forming  ammonium 
carbonate  and  calcium  sulphate.  This  is  sometimes 
called  "double  decomposition."* 

135.    Laws   of    Double   Decomposition.— 

Berthollet's  laws  may  be  stated  as  follows  :t 
{a).  Whenever  in  a  mixture  of  two  or  more 
substances  it  is  possible  by  a  rearrangement  of 
the  radicals  to  form  a  compound,  volatile  at 
the  temperature  of  the  experiment,  such  rear- 
rangement will  occur  and  the  volatile  com- 
pound will  be  formed,  {b).  Whenever  on 
mixing  two  or  more  substances  in  solution,  it 
is  possible,  by  rearrangement  of  the  radicals, 
to  form  an  insolublej  compound,  that  rear- 
rangement will  occur  and  the  insoluble  com- 
pound will  be  formed  as  a  precipitate. 

In  other  words  if  solutions  of  two  salts  be  mixed,  and 
by  double  decomposition  an  insoluble  salt  can  be  formed, 
the  double  decomposition  will  take  place  and  the  insolu- 
ble salt  will  be  formed.  If  the  salt  be  only  difficultly 
soluble,   the  double  decomposition  will  take  place   be- 

*Professor  J.  H.  Salisbury  explains  double  decomposition  as  fol- 
lows: in  many  cases  of  substitution  the  element  displaced  combines 
with  the  element  or  radical  with  which  the  displacing  element  was 
previously  combined  and  two  new  compounds  are  formed  in  which 
the  radicals  have  changed  places  with  each  other.  When  com- 
pounds of  two  basylous  radicals  or  metals  are  brought  together  in 
solution,  a  double  decomposition  occurs,  consisting  in  change  of 
place  on  part  of  the  metals  or  basylous  radicals  with  each  other. 

"I"  Woody, 

tinsoluble  in  the  menstruum  present. 


•70  DENTAL  CHEMISTRY. 

tween  concentrated  solutions,  but  not  between  dilute.  If 
by  double  decomposition  a  volatile  substance  can  be 
formed,  the  double  decomposition  will  take  place  and 
the  substance  will  be  formed.  If  the  volatile  substance 
is  soluble  in  water,  the  double  decomposition  may  not 
take  place  until  the  solutions  are  concentrated,  or  until 
the  substances  are  entirely  deprived  of  water.  For  exam- 
ple, sodium  nitrate  and  sulphuric  acid  may  exist  together 
in  dilute  solution,  but  upon  concentration  double  decom- 
position takes  place,  the  volatile  nitric  acid  being  given 
off.* 

The  insoluble  compound  formed  by  double  decomposi- 
tion separates  from  the  solution  as  2, precipitate. 

In  order  that  the  student  may  become  familiar  with 
the  principle  of  the  laws,  it  is  necessary  that  the  principal 
insoluble  and  volatile  compounds  be  known. 

Inorganic  Compounds  Insoluble  in  Water. 

1.  Most  compounds  of  the  heavy  metals. 

2.  Almost  all  oxides, 

3.  Nearly  all  carbonates  and  phosphates. 

Exceptions. 

I.  Chlorides,  sulphates,  chlorates,  and  nitrates  are  sol- 
uble, but  lead  chloride,  mercurous  chloride,  and  silver 
chloride  are  insoluble;  barium  sulphate  and  strontium 
sulphate  are  insoluble;  oxides,  hydrates,  sulphides,  and 
iodides  of  the  alkaliesf  and  alkaline  earths;}:  are  not  in- 
soluble. 

136.  Important  Volatile  Compounds.  —  Ammonia, 
carbonic  acid,  nitric  acid,  hydrochloric  acid,  sulphur- 
etted hydrogen. 

Example  18.     How   may   lead  sulphate   be    made   by 

*J.  H,  Salisbury. 
tK,  Na,  NH4 , 
JCa,  Ba,  Sr. 


CHEMICAL    PHILOSOPHY. 


71 


double  decomposition?     Calcic  carbonate?     Barium  sul- 
phate?    Silver  chloride? 

Answers.  From  hydrogen  sulphate,  or  a  soluble  sul- 
phate, and  lead  nitrate  or  other  soluble  salt  of  lead.  From 
sodium  carbonate  and  calcium  chloride.  From  barium 
— — and sulphate.  From  silver and  hydro- 
gen   . 


137.  Modes  of  Decomposition. — The  separation  of  a 
compound  body  into  its  constituent  elements  may  be  pro- 
duced in  various  ways: 

1.  By  heat:  when  limestone  is  heated,  it  is  decom- 
posed into  lime  and  carbonic  acid.  Chemically  speaking, 
calcium  carbonate  is  decomposed  by  heat  into  calcium 
oxide  and  carbon  dioxide.  When  an  amalgam  is  heated, 
it  is  separated  into  mercury,  which  is  driven  off,  and  some 
other  metal  or  metals. 

2.  By  electricity:  electricity  decomposes  many  sub- 
stances, provided  they  are  in  a  liquid  or  gaseous  state. 
Hydrochloric  acid  gas  may  be  decomposed  by  passing 
an  electric  spark  through  it;  water,  by  passing  an  electric 
current  through  it.  Solutions  of  the  metals  may  be  de- 
composed by  electricity  and  the  metals  themselves  de- 
posited.   (See  Copper  Amalgam). 

4.     By  light:  see  Section  83. 

138.  Chemical  Equations.  -- These  repre- 
sent what  actually  takes  place  in  a  reaction. 
The  sum  of  the  weights  of  the  factors  is  al- 
ways equal  to  the  sum  of  the  weights  of  the 

products. 
Rule  16.    To  write  Chemical  Equations. — 

1.  Write  formulae  of  factors. 

2.  Connect  formulae  of  factors  by  plus 
sign. 


DENTAL   CHEMISTRY. 


3.  Write  formulae  of  products,  connected 
by  sign  of  plus. 

4.  Between  factors  and  products  write  the 
sign  =. 

Thus,  silver  nitrate  and  hydrogen  chloride 
give  silver  chloride  and  hydrogen  nitrate; 
to  represent  the  reaction  by  an  equation: 

1.  Formulae  of  factors:  AgNOa,  HCl. 

2.  Connected  by  plus  sign:  AgNOa,  +  HCl. 

3.  Formulae  of  products:  AgCl,  HNO3. 

4.  Connected  by  plus  sign:   AgCl  +  HNO3. 

5.  2  and  4  placed  equal  to  one  another: 

AgNOa  +  HCl  =  AgCl  +  HXO3. 
finles  for  determining  the  changes  which  take  place 
in  chemical  reactions. — To  decide  why,  for  example,  sil- 
ver nitrate  and  hydrogen  chloride  give  silver  chloride 
and  hydrogen  nitrate,  certain  rules' should  be  committed 
to  memory: 

1.  Find  out  which  elements  or  radicals  are  positive 
and  which  negative.  [In  the  above  equation  in  the  left 
hand  member  we  find  the  metal,  silver,  (Table  i )  positive, 
the  radical,  NO3,  negative,  (Table  4). Hydrogen  is  positive 
and  chlorine  negative.  (See  Table  i).  Positives  combine 
with  negatives  and  vice  versa,  hence  on  the  right  hand 
side  in  the  products,  Ag  will  be  found  with  CI,  and  not 
with  H,  and  the  latter  with  NO3,  and  not  with  Ag]. 

2.  Cause  the  positives  to  change  places. 

3.  Pay  due  attention  to  quantivalence.  [In  the  above 
equation,  Ag  being  monad  can  take  the  place  of  H  to 
form  AgCl,  and  H  being  monad  can  take  the  place  of  Ag 
to  form  HNO3]. 

4.  Notice  that  compound  radicals  usually  remain  un- 
changed in  products. 


CHEMICAL   PHILOSOPHY.  73 

5.  N.  B.  An  acid  and  an  alkali  cannot  exist  free  in 
the  same  solution,  and  the  strongest  acid  usually  selects 
the  strongest  base  with  which  to  combine. 

Example  19.     Complete  the  following  equations: 

1.  Zn  +  H2SO,  =  ? 

2.  (NHO^SO,  +  CaC03=? 

3.  H, +  C1,=  ? 

4.  (NaCl)2+  H2SO,  =  ? 

5.  (KC103).  =  ? 

6.  FeS  +  HaSOi  =  ? 

7.  S  +  O,  =  ? 

8.  P,05+  (H,0)3=  ? 

9.  CaCOa  =  ? 

ANSWERS. 

2.     CaSOi  H . 

8.  H6P208or . 

9.  CaO  H . 

Example  20.  In  example  18  give  two  equations  illus- 
trating each  answer. 

139.  Chemical  Arithmetic. — By  use  of  equations  we 
may  calculate  the  weight  of  any  substance  required  by 
any  given  process.  The  rule  is,  as  the  formula  of  the 
given  substance  is  to  the  formula  of  the  required  sub- 
stance so  is  the  weight  of  the  given  substance  to  the 
weight  of  the  required  substance.  Thus,  how  much  sul- 
phate of  zinc  can  be  made  from  5  pounds  of  zinc? 

Reaction:     Zn  +  H.SO  =  ZnSOi  +  H2. 

Proportion:     Zn:      ZnS04  =  5  :  x. 

Reduced  to  figures:     65  :  161  =  5  :  x. 

Product  of  means  put  equal  to  that  of  extremes:     65  x 

=  161  X  5. 

Algebraically:     x  =  ^"e^^  =  \?  =  12.3  lbs. 

Note:  after  the    formulae   are   written    in  the    proper 


74  DENTAL   CHEMISTRY. 

proportion,   the   molecular    weights  are    substituted  for 
them. 

140.  Relations  of  Chemical  Change  to  Force.— Chemi- 
cal change  is  accompanied  by  heat,  electricity,  often  by 
light,  and  bears  a  relation  to  vital  force. 

Solution  is  accompanied  by  heat,  as  when  caustic  soda  is 
dissolved  in  water. 

Neutralization  is  accompanied  by  heat,  as  when  sodium 
hydrate  is  added  to  sulphuric  acid. 

Chemical  action  is  accompanied  by  heat,  as  when  sul- 
phuric acid  acts  on  zinc. 

Precipitation  is  accompanied  by  heat,  as  when  copper 
sulphate  solution  is  precipitated  by  a  strip  of  zinc* 

The  heat  evolved  in  any  chemical  process  is 
a  measure  of  its  energy,  and  the  tendency  is 
toward  those  combinations  and  conditions 
which  involve  the  greatest  evolution  of  heat. 

141.  Light. — The  luminous  effects  witnessed  in  many 
chemical  combinations  are  due  to  the  high  temperature 
produced.  Luminous  flames  are  nothing  more  than  gas- 
eous matters  containing  solids  heated  to  the  point  of  in- 
candescence. 

142.  Electricity. — All  chemical  reactions  are  accom- 
panied by  a  disturbance  of  electrical  equilibrium.  Chemical 
reactions  between  metals  and  liquids  are  the  most  produc- 
tive of  electricity.  When  a  liquid  acts  chemically  on  a 
metal,  the  liquid  assumes  the  positive  electrical  condition 
and  the  metal  the  negative. 

A  galvanic  current  is  produced  whenever  two  metals 
are  pjaced  in  metallic  contact  in  a  liquid  which  acts  more 
powerfully  on  one  than  on  the  other. 


♦The  heat  is  not  always  perceptible  in  all  cases,  and  to  measure  it 
an  instrument  called  a  calorimeter  should  be  used. 


CHEMICAL   PHILOSOPHY.  75 

143.  A^ital  Force. — An  uninterrupted  succession  of 
chemical  reactions  goes  on  in  the  living  body.  New 
molecules  are  constantly  arriving  and  old  ones  departing. 
Almost  every  vital  act  in  the  body  may  be  said  to  be 
accomplished  by  oxidation,  and  therefore  by  a  consump- 
tion of  oxygen.  Between  the  food  and  the  absorbed 
oxygen  an  interplay  of  changes  is  essential  to  the  main- 
tenance of  the  vital  functions,  whether  these  consist  in  the 
production  of  heat,  in  muscular  contraction,  in  mental 
activity,  or  in  assimilation.  The  ultimate  products  of 
oxidation  in  the  body  are  urea,  carbonic  acid,  and  water. 

144.  Chemical  Affinity. — Bodies  most  opposed  to 
each  other  in  chemical  properties  evince  the  greatest  ten- 
dency to  combine  together,  and  conversely.  The  metals 
and  hydrogen  have  strong  affinity  for  oxygen,  chlorine, 
and  iodine,  but  the  attraction  of  metals  for  one  another 
is  more  feeble  by  far,  as  is  also  the  attraction  of  chlorine 
for  iodine,  etc.,  etc.  Acids  are  drawn  toward  alkalies, 
and  alkalies  toward  acids. 

145.  Circumstances  influencing  Cliemical 
Attraction.  —  (a)  Alteration  of  temperature: 
mercury  absorbs  oxygen  at  one  temperature 
but  gives  it  off  at  a  higher  one.  (d)  Solution: 
tendency  toward  formation  of  a  substance  m- 
solitble  in  the  medium  of  solution.  (<;)  Heat: 
tendency  toward  formation  of  a  volatile  com- 
pound when  substances  are  mixed  and  heated. 
(</)  Nascent  state:  substances  combine  better 
in  the  7iascent  state,  that  is,  when  each  is  simul- 
taneously liberated  from  some  previous 
combination.  (<?)  Influence  of  abase:  as,  for 
example,  oxidation  of  platinum  by  fused  po- 


DENTAL   CHEMISTRY. 


tassium  hydrate.    (/)  Mere  presence  of  certain 
bodies  as  ferments.    (See  Fermentation). 

Porous  bodies  by  their  presence  favor  certain  chemical 
change.  Hydrogen  and  vapor  of  iodine  mixed  in  a  tube 
heated  to  redness  do  not  combine,  but  immediately  unite 
if  spongy  platinum  be  present  with  them.  This  change 
may  be  classified  under  catalytic  action  and  further  ex- 
amples are  not  necessary. 

Heat,  light,  and  electricity  are  favorable  to  chemical 
change.  Moreover,  the  physical  condition  of  bodies,  and 
pressure  dCTQ  to  be  reckoned  as  factors.  Chemical  change  be- 
tween substances  in  liquid  or  gaseous  state,  as  a  rule.is  more 
easily  brought  about  than  when  the  substances  are  in  the 
solid  state.  For  example,  tartaric  acid  and  bicarbonate 
of  sodium,  if  mixed  dry,  do  not  effervesce,  but  imme- 
diately do  so  when  water  is  added. 

Pressure  arrests  certain  changes,  notably,  such  as  give 
rise  to  disengagement  of  gas.  Thus,  zinc  is  not  attacked 
so  well  by  acids  in  a  closed  tube  as  in  an  open  one,  owing 
to  the  pressure  of  the  disengaged  hydrogen.  Pure  zinc 
is  not  attacked  by  pure  sulphuric  acid,  owing  to  conden- 
sation of  gas  on  the  surface  of  the  metal.  Pressure  facili- 
tates certain  changes:  under  pressure  chloride  and  ni- 
trate of  silver  are  decomposed  by  hydrogen;  silver  is 
displaced  and  hydrochloric  acid  or  nitric  acid  formed. 
Under  pressure  of  20  atmospheres,  an  alcohol  flame  be- 
comes as  bright  as  that  of  a  candle. 

146.  Classification  of  the  Elements.— It  is  difficult 
to  classify  the  elements  in  a  manner  which  shall  be  en- 
tirely satisfactory. 

There  are  a  number  of  well-marked  groups  in  which 
there  is  some  connection  between  the  atomic  weights  and 
the  properties  of  the  elements;  as,  for  example,  in  one 
group  chlorine,  bromine,  iodine;  in  another,  sulphur,  sele- 
nium, tellurium;  in  a  third,  lithium,  sodium,  potassium. 


CHEMICAL   PHILOSOPHY.  77 

If  in  each  of  these  groups  the  atomic  weights  of  the  first 
and  last  be  added,  and  the  sum  divided  by  2,  there  results 
very  nearly  the  atomic  weights  of  the  middle  members. 
Moreover,  the  chemical  properties  of  an  element  in  each 
group  are  much  like  those  of  others  of  the  same  group. 
Mendeleef  has  shown  that,  if  all  the  light  elements  of 
atomic  weights  from  7  to  36  be  arranged  in  the  order  of 
their  atomic  weights,  the  result  is  as  follows: 

I.  Li  =  7;  Be  =  9;  B=  11;  C  =  12;  N  =  14;  O  =  16; 
Fl  =  19. 

il.  Na  =  23;  Mg  =  24;  Al  =  27;  Si  =28;  P  =  31; 
5  =  32;  CI  =  35.5. 

Proceeding  from  left  to  right,  there  is  a  gradual  change  in 
the  properties  of  members  of  the  series;  basic  properties 
grow  weaker  and  acid  properties  stronger;  the  metals  are 
at  the  left  end,  the  non-metals  at  the  right,  and  those 
classed  sometimes  with  metals,  sometimes  with  non- 
metals,  in  the  middle,  as,  for  example,  silicon. 

All  the  elements  may  be  arranged  in  series  like  the 
above.  The  changes  in  the  properties  of  the  elements 
will  be  noticed  to  he  periodic;  that  is,  they  change  accord- 
ing to  the  increasing  atomic  weights,  and  are  then  re- 
peated in  a  nczv  period. 

Corresponding  members  of  the  even  periods  or  of  un- 
even periods  resemble  one  another  more  closely  than  the 
members  of  the  even  periods  resemble  those  of  the  un- 
even periods;  that  is,  for  example,  those  of  the  4th  and 
6th  are  more  alike  than  they  are  to  those  of  5th  and  7th, 
and  those  of  5th  and  7th  resemble  each  other  closely. 

For  further  consideration  of  the  periodic  law  the  reader  is  referred 
to  "Remsen's  Theoretical  Chemistry."  Other  authorities  are  Meyer, 
Ostwald,  Hortsmann,  and  M.  M.  Pattison  Muir.  The  work  of  Muir 
on  the  Principles  of  Chemistry  will  be  an  aid  to  those  who  are  not 
familiar  with  the  German  language. 


DENTAL    CHEMISTRY. 


H 


'V 

c 


3 


II 

«-           -^   II 

§    1 

1    ^  11 

^            1       1 

>    ;^ 

0 
U 

2       c^^ 

11 

^•&: 

11 

a|0 

to" 

buo 

05      - 

3 

§•'3: 

2 

II 

zii    To 

< 

11  2 

< 

0 

g'3  ^11 

0        1 

1     <"  1, 
1     0  11 

•o" 

05                   1 
rH            1       1 

>q 

0 

t» 

1 

1 

!x5 

CJ 

to 

II  •« 

00 

llg 

C4 

1-H 

11 

1 

1 

0 

1-1 
II 

II 

1 

I— « 

1 

1 

1 

04 

S5 

0 

1 

1 

CO 

r^ 

1 

1 

0 

^11 

C/3  <N 

II 

00 

0 

I-H 
II 

II 

CO  II 
0 

11 

II 

0 

u 

s 

1 

^ 

D 

rH 

»Q 

0 

1 

X) 

w 

t>. 

•N 

1 

0 

II 
II 

II. 

^11 

J3 

T-l 

M 

cccO 

I-H 

II 

11^ 

^11 

00 

rH 

II 

11 

Z 

> 

Z 

5 

H 

00 

iM 

00 

1 

t- 

SM 

t- 

1-H 

1 

0 

§2:  as 
0 

rH 
II 

II 

II 

II 

(u  0 

1s 

c/)l| 

IN 

II  ^ 

eull 

J3 

u 

P 

N 

U 

1 

H 

t- 

0 

TO 

i 

•<*| 

eq 

t* 

rH 

1 

0 

11 
0 

rH 

M 

ill 

0 

I-l 

II 

II 
rt  05 

II 

llg 

TO 

rH 

II 
J3 

Jl 

CQ 

in 

> 

J 

> 

1 

■* 

»a 

i^ 

1 

^-s 

IM 

<x> 

rH 

1 

0 

^ 

II 

11 

rH 

N 

a  1  0 

« 

II   TO 

II 

glos 
0 

II 

^11 

tsjoo 

ST 

bo 

<u 

rt 

>M 

ei 

n 

U 

Cfi. 

an 

1 

1 

1-t 

TO 

S«l 

TO 

cc 

tt 

!l 

11 

«0 

0 

! 

a    0 
1'^ 

II 

11.0 
3* 

y^ll 

.a 

lis 

^11 

rH 

II 

3 

0 

II 

< 

Ij 

^ 

a; 

u 

1 

1 

•sauas 

11  eq 

«■* 

10  ;o 

t-  » 

C5  0 

—  rt 

CHEMICAL    PHILOSOPHY. 


79 


Explanation  of  Table  I. 
R  denotes  the  symbol  of  any  element  in  the  group. 
R2  O  would  mean  that  in  uniting  with  oxygen,  two  atoms 
of  any  element  in  the  group  unite  with  one  of  oxygen. 
Each  series  is  called  a  small  period.  Series  i  and  2  form 
the  first  large  period;  series  3  and  4  the  second,  and  so  on. 

No.  II. 


I. 

II. 

III. 

IV. 

V. 

VI. 

R20 

I. 

Li=7 

K 

39 

Rb    85 

Cs  133 

—       — 

—       — 

RO 

11. 

Be=9 

Ca 

40 

Sr    87 

Ba  137 

-       - 

—       - 

R2O3 

III. 

B    11 

Se 

44 

Y    89 

La  139 

Yb  173 

-       — 

RO2 

IV. 

(H^C) 

C-12 

Ti 

48 

Zr    90 

Ce  142 

-       - 

Th  231 

RaOs 

V. 

(H3N) 

N=U 

V 

51 

Nb    94 

Di  145 

Ta  182 

—       — 

R03 

VI. 

(HaO) 

0=16 

Cr 

52 

Mo    96 

-       - 

W184 

U    240 

RaO, 

VII. 

(HF) 

F=19 

Mn 

55 

-       - 



-       - 

-        - 

Fe 

56 

Ru  103 

-       - 

Os  195? 

-        - 

RO4 

VIII. 

Co 

E9 

Rh  104 

_ 

Ir  193 

-        — 

Ni 

59 

Pd  106 

-       - 

Pt  195 

-        - 

RaO 

I. 

n. 

H=l 

Na=23 

Cu 

Zn 

63 
65 

Ag  108 
Cd  112 

Au  197 
Hg  200 

-       - 

RO 

Mg    24 

-        - 

RaOs 

III. 

AI    27 

Ga 

70 

In  113 

-       - 

TI  204 

-        - 

ROa 

IV. 

(H4R) 

Si    28 

Ge 

72 

Sn  118 

-       - 

Pb  207 

-        - 

RaOs 

V. 

(HaR) 

P    31 

As 

75 

Sb  120 

-       - 

Bi  208 

-        - 

ROa 

VI. 

(HaR) 

S    32 

Se 

79 

Te  126 

-       - 

-        - 

-        - 

Ra07 

VII. 

(HR) 

CI  85.5 

Br 

80 

I    127 

-       - 

-        - 

-        - 

Explanation:  in  Table  II  the  elements  are  in  groups, 
but  in  such  a  way  as  to  indicate  the  difference  between 
the  even  and  uneven  periods.  Thus  at  the  top  in  line  with, 
and  to  the  right  of  RgO,  I,  will  be  seen  from  left  to  right, 
the  members  of  the  even  series:  Li,  K,  Rb,  etc.,  which 
belong  to  series  2,  4,  6,  etc. 

Then  aft'er  those  of  the  even  series  have  been   finished 


DENTAL  CHEMISTRY. 


80 

those  of  the  odd  are  taken  up,  beginning  with  H  and  go- 
ing on  to  Na,  Cu,  etc.,  from  left  to  right. 

In  other  words  corresponding  members  of  even  periods 
are  given  first,  then  corresponding  members  of  odd 
periods. 

147.  Meyer's  Classification.— Lothar  Meyer  arranges 
the  periods  somewhat  differently,  not  in  horizontal  lines, 
but  in  lines  so  inclined  that,  if  the  table  were  pasted  on  a 
cylinder  of  the  right  size,  the  table  would  form  a  contin- 
uous spiral,  beginning  at  the  top  with  lithium,  and  ending 
at  the  bottom  with  uranium.  Meyer  has  shown  a  very 
close  connection  to  exist  between  the  atomic  weights  and 
various  properties  of  the  elements. 


The  work  of  Mendeleef,  and  also  of  Meyer,  has  been  of  the 
greatest  interest  to  chemists.  The  author  has  not  thought  it  desir- 
able to  go  further  into  details  concerning  the  various  classifications 
of  the  elements  in  a  book  like  a  Dental  Chemistry,  which  is  essen- 
tially practical  in  nature  and  limited  in  scope.  But  it  is  very  desir- 
able that  those  intending  to  teach  chemistry  should  familiarize 
themselves  as  thoroughly  as  possible  with  the  theoretical  principles 
of  the  science.  For  this  purpose  the  following  books  should  be 
owned:  J.  P.  Cooke's  "Chemical  Philosophy"  and  "New  Chemistry"; 
Lothar  Meyer's  '"Modern  Theories  of  Chemistry",  elsewhere  referred 
to;  M.  M.  Pattison  Muir's  "Treatise  on  the  Principles  of  Chemistry.'' 
German  text-books  of  value  are  Ostwald's  "Lehrbuch  der  Allgemeinen 
Chemie",  and  A.  Horstman's  "Theoretische  Chemie"  to  be  found  in 
Band  I.  2.  Graham-Otto's  "Ausfiihrliches  Lehrbuch  der  Chemie.'' 
[Wohler's  "Outlines  of  Organic  Chemistry"  has  been  translated 
from  the  8th  German  edition  by  Professor  Remsen,  and  is  useful  in 
studying  the  Carbon  Compounds],  Going  into  more  special  works 
of  interest  to  the  dentist,  we  find  Krupp's  "Die  Legirungen".  to  be 
had  in  English  with  additions  under  the  name  of  "The  Metallic 
Alloys"  by  W.  T.  Brannt.  There  is  also  a  work  known  as  the 
"Techno-Chemical  Receipt  Book",  which  may  prove  handy  for 
reference  at  times  in  regard  to  matters  purely  practical.  But  the 
subject  of  chemistry  as  a  whole  can  not  be  intelligently  compre- 
hended until  very  diligent  study  has  been  given  to  theory. 


CHEMICAL    PHILOSOPHY. 


81 


Table  8. 
Lothar  Meyer's  Arrangement  of  the  Jilements. 


I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

VIII. 

Li 

Be 
9.08 

7.01 

B 
10.9 

c 

11.97 

N 
14.01 

0 
15.96 

Na 

F 
19.06 

Mg 
23.94 

22.99 

AI 
27.04 

Si 
28 

P 
30.96 

S 

31.98 

Cr 
52.45 

K 

CI 
35.37 

Ca 
39.91 

39  03 

Sc 
43.97 

Ti 
48 

V 
51.1 

Cu 

Mn 
54.8 

Zn 

64.88 

Fe 

55.88 

Co 
58.6 

63.18 

Ga 
69.9 

Ni 

Ge 
72.32 

As 
74.9 

58  6 

Se 

78.87 

Rb 

85.2 

Br 
79.76 

' 

Sr 
87.3 

?Y 
89.6 

Zr 
93.4 

Nb 
93.7 

Mo 
95.9 

Ag 
107.66 

? 
99 

Cd 
111.7 

Ru       Rh 
103  6     104  1 

Pd 

In 
113.4 

Sn 
117.35 

Sb 
119.6 

lOfi  9! 

Te 
126.3 

Cs 
132.7 

I 
126.54 

Ba 
136.86 

La 
138.^ 

Ce 
141.2 

Di? 
145 

? 
151 

? 

? 
152 

165 

? 
170 

Yb 
172.6 

? 
176 

Ta 

182 

W 
183.6 

Au 
196.2 

? 
185 

Hg 
199.8 

Os 
195? 

Ir 
192.5 

Pt 

TI 
203.7 

Pb 
206.39 

?Th 
231.96 

Bi 
207.5 

194.3 

? 
210 

?u 

239.8 

? 

? 
211 

? 
226 

222 

? 
230 

? 
234 

The  spaces  left  blank  are  to  be  filled  with  elements  yet 
to  be  discovered.* 


♦Mendeleef  predicted  the  discovery  of  an   element  between  cal- 
cium and  titanium.    Scandium  was  discovered   and  filled  the  place. 


CO  DENTAL   CHEMISTRY. 

148.  General  Properties  of  the  Metallic 
Elements.— Metals  are,  as  has  already  been 
seen,  elementary  bodies,  solids  with  exception 
of  mercury,  insoluble  in  water,  and  possessed 
of  certain  properties  as  lustre,  fusibility,  etc. 
Among:  the  more  important  properties  of 
metals  we  fmd 

/;«5/;?r,— power  of  reflecting- light; 

/^;/aa/v,— resistance  to  any  attempt  to  pull 
asunder  their  particles; 

;;/^//^<^/^////)^— capability  of  being;  hammered 
or  rolled  into  thin  sheets; 

ductility, — property  of  being  drawn  out  into 
wire; 

high  specific  gravity, — or  weig-ht  relative  to 
water;* 

high  conducting  power, — for  heat  and  elec- 
tricity; 

fusibility, — property  of  becoming  liquid  when 
heated; 

capacity  for  heat,  or  specific  heat; 

expansibility, — property  of  expanding  when 
heated; 

crystalline  structure, — shown  by  metals  on 
cooling  from  fusion; 


♦Only  seven  have  a  sp.  gr.  below  6.72,  but  tliry  \  ary  irom  osmium, 
22,  to  lithium,  0.59. 


CHEMICAL    PHILOSOPHY.  83 

volatility, — property  of  being  converted  into 
vapor; 
color  ; 
odor  and  taste. 

149.  The  most  lustrous  metals  are  gold,  silver,  plati- 
num, palladium,  steel,  aluminium;  zinc  and  lead  are  infe- 
rior in  lustre;  tin  is  naturally  a  brilliant  metal,  but  not 
hard  enough  to  be  polished  like  steel. 

150.  The  specific  heat  of  metals  is  the  amount  of 
heat  necessary  to  raise  equal  weights  of  different  metals 
from  the  same  given  temperature  to  another  given  tem- 
perature. Water  is  assumed  as  the  standard,  and  we  find 
that  the  capacity  for  heat  of  the  different  metals  is  in  the 
following  order:  iron,  nickel,  cobalt,  zinc,  copper,  palladi- 
um, silver,  cadmium,  tin,  antimony,  gold,  lead,  platinum, 
bismuth.  Suppose,  now,  a  cubic  inch  of  iron  and  a  cubic 
inch  of  tin  were  both  heated  to  the  same  temperature  for 
the  same  time  and  placed  each  on  a  cake  of  parafifine, 
which  would  melt  its  cake  the  sooner?  Iron,  because  its 
capacity  for  heat  is  greater  than  that  of  tin. 

151.  All  metals  are  somewhat  volatile:  some  are  no- 
ticeably volatile,  as  mercury,  arsenic;  others  to  a  limited 
extent,  and  a  few  with  difficulty  even  at  highest  tempera- 
tures. Gold  is  somewhat  volatile  when  alloyed  with  cer- 
tain metals. 

152.  The  characteristic  color  of  metals  ranges  from 
pure  white  to  bluish.*  A  few  metals,  as  iron,  copper,  and 
zinc  have  an  odor,  especially  when  heated. 

153.  The  noble  metals  are  mercury,  silver,  gold,  plat- 
inum, palladium,  rhodium,  ruthenium,  osmium,  iridium; 
they  may  be  separated  from  their  oxides  by  merely  heat- 
ing to  redness. 

*Lead  is  feebly  tinted  with  blue,  bismuth  with  pink,  calcium  with 

yellow. 


34  DENTAL   CHEMISTRY 

1 54.  The  decomposition  of  acids  by  metals  and  re- 
placement of  hydrogen  has  already  been  alluded  to. 

155.  Metals  are  opaque,  except  gold  which  if  in  thin 
leaves,  transmits  a  greenish  or  purplish  light. 

156.  Metals  are  nearly  all  sectile;  that  is,  when  cut 
with  a  knife  they  do  not  crumble.  For  example,  gold  is 
perfectly  sectile,  but  pyrites  and  other  minerals  like  it 
crumble  under  the  knife. 

Metals  can  be  fused  together  and  unite  in  all  propor- 
tions forming  alloys. 

157.  The  metallic  elements  used  in  dentistry  will  oe 
tabulated  with  reference  to  their  symbols,  Latin  names, 
valence,  specific  gravity,  etc.,  etc.  Before  studying  them, 
certain  definitions  and  explanations  are  necessary. 

Fusing  point:  the  temperature  at  which  the  various 
metals  melt  and  become  liquid.  Lead  melts  at  617° 
Fahrenheit,  hence  its  fusing  point  is  said  to  be  617°. 

Length  of  bar  at  212^^  F.,  which  measures  i  at  32^  F.  It 
is  well  known  that  heat  expands  metals:  thus,  a  bar  of 
aluminium,  which  at  32°  F.  is  i  foot  long,  at  212°  F.  will  be 
I  ma  foot.  In  the  tabulated  statements  concerning 
length  of  bar  in  metals,  fourteen,  namely:  aluminium,  an- 
timony, bismuth,  cadmium,  copper,  gold,  iron,  lead,  mag- 
nesium, palladium,  platinum,  silver,  tin,  and  zinc  are  con- 
sidered. Given  any  unit  of  measurement  then,  whether  an 
inch,  a  foot,  etc.,  etc.,  there  will  be  at  212°  F.  a  cer- 
tain gain  in  length  of  the  bar.  It  must,  however,  be 
remembered  that,  for  the  same  kind  of  metal,  the  greater 
its  specific  gravity  the  greater  its  expansion  for  a  given 
increase  in  temperature. 

Tensile  streiigth*  is  the  resistance  of  the  fibres  or  particles 

♦Under  tensile  strength  the  absolute  tenacity  of  the  metal  is  ex- 
pressed in  figures,  while  under  tenacity  it  is  expressed  relatively 
as  regards  other  metals. 


CHEMICAL    PHILOSOPHY, 


of  a  body  to  separation,  and  the  amount  of  weight  or 
power  required  to  tear  asunder  one  square  inch  of  a  metal 
is  given,  in  figures,  in  tons;  thus,  the  tensile  strength  of 
iron  (wrought)  is  said  to  be  29.  This  means  that  a  weight 
of  29  tons,  or  a  power  equivalent  to  29  tons,  is  necessary 
to  tear  asunder  one  square  inch  of  the  metal. 

Tenacity,  the  metals  are  compared  as  regards  tenacity 
with  lead,  which  is  the  weakest;  the  tenacity  of  copper  is 
said  to  be  18,  which  means  that  it  is  18  times  more  tena- 
cious than  lead;  copper  is  said  to  be  in  "3d  rank,"  because 
of  the  ten  metals,  steel,  iron,  copper,  platinum,  silver, 
gold,  palladium,  zinc,  tin,  lead,  there  are  only  two  which 
are  more  tenacious.  Care  should  be  taken  to  note  that  the 
"rank"  of  a  metal  is  strictly  relative,  and,  unless  the  metals 
with  which  it  is  compared  be  known,  the  idea  conveyed 
by  the  term  is  wholly  vague. 

Malleability :  the  metals  are  compared  with  gold, 
which  is  the  most  malleable;  n^/?^  metals  in  all  are  com- 
pared, namely:  gold,  silver,  copper,  tin,  platinum,  lead, 
zinc,  iron.  The  malleability  of  zinc  is  said  to  be  7,  which 
means  that  there  are  six  metals  more  malleable;  its  rank, 
therefore,  among  the  eight,  is  7th. 

Ductility:  the  standard  is  gold  which  is  the  most  duc- 
tile. Ten  metals  are  compared:  gold,  silver,  platinum, 
iron,  copper,  palladium,  aluminium,  zinc,  tin,  iron.  The 
ductility  of  zinc  is  said  to  be  8,  which  means  that  seven  of 
the  ten  metals  are  more  ductile.  It  is  therefore  8th  in 
rank.  //  will  be  noticed  that  the  comparison  in  regard  to  tenac- 
ity is  made  differently  from  either  that  in  regard  to  malleability 
or  to  ductility. 

Conducting  power  with  reference  to  heat:  the  metals 
are  compared  with  silver,  which  is  the  best  conductor,  and 
eleveti  metals  in  all  are  considered;  the  conducting  power 
of  zinc  is  said  to  be  5,  which  means  that  four  metals  are 
better  conductors;  it  is,  therefore,  5th  in  rank. 


ort  DENTAL   CHEMISTRY. 

Conducting  poivcr  with  reference  to  electricity:  the 
metals  are  compared  with  silver,  which  is  the  best  con- 
ductor of  electricity.  Twelve  metals  are  considered, 
namely:  silver,  gold,  copper,  zinc,  palladium,  platinum, 
iron,  nickel,  tin,  lead,  antimony,  bismuth.  The  conduct- 
ing power  of  zinc  for  electricity  is  290,  silver  being  taken 
as  1,000  in  conducting  power.  In  other  words,  silver  is 
^my  or  3.44,  times  a  better  conductor  than  zinc.  But  zinc 
is  4th  in  rank  among  the  twelve,  for  only  three  are  better 
conductors  of  electricity. 

Resistance  to  air,  etc:  resistance  to  dry,  pure  air  is  one 
thing,  but  resistance  to  air  containing  moisture,  carbonic 
acid,  etc.,  is  quite  another.  Under  this  head  also,  is 
mentioned  the  effect  of  sulphuretted  hydrogen  on  the 
metal. 

Solubility:  under  this  head  the  best  solvents  for  the 
metal  are  given,  that  is,  substances  having  the  power,  like 
acids,  to  attack  the  metal  and  convert  it  into  a  liquid. 

Direct  combinations :  under  this  heading  is  given  a  list 
of  substances  which  unite  directly  with  the  metal,  either 
in  the  cold  or  when  heated,  rubbed,  or  triturated  with  it, 
without  the  intervention  of  oxygen. 

Structure:  many  of  the  metals  have  a  crystalline  struc- 
ture, i.  e.,  when  small  particles  of  them  are  seen  under  the 
microscope,  certain  definite  geometrical  shapes  are  ob- 
served as  cubes,  rhombohedrons,  etc.  The  form  in  which 
iron  tends  to  crystallize  is  a  regular  octahedron:  an  eight- 
sided  figure  with  equal  axes  at  right  angles  to  one  an- 
other. Crystalline  forms  are  classified  into  six  systems. 
(See  Chap.  I).  Many  of  the  metals  are  to  be  found  in 
the  first  or  isometric  system,  in  which  there  are  three  axes 
of  equal  length,  and  at  right  angles  to  each  other,  as  in 
case  of  the  cube  and  the  octahedron.  Copper  crystals 
are  examples  of  the  isometric  system. 

Compounds:  the   metals   form    various    compounds  ac- 


CHEMICAL    PHILOSOPHY. 


87 


cording  to  their  equivalence,  and  Latin  names  are  often 
used  instead  of  English:  for  example,  iron  as  a  dyad, 
uniting  with  other  elements,  forms y^;r^z^.y  compounds;- sil- 
ver compounds  are  sometimes  called  argentic,  as  argentic 
nitrate,  etc.,  etc. 

Table  No.  9 — Names  and  Properties  of  the  More 
Important  Metals. 


Names. 

Sp.  gr. 

Fusing  Point; 
approximate 
Fahrenheit. 

Weight  of  One 
Cubic  Foot 
in    Pounds. 

Tensile  Str'gth 

per  sq-  inch 

in  tons. 

♦Aluminium 

Antimony 

Bismuth 

2.67 

6.72 

9.80 

8.69 

8.51 

8.95 

19.34 

7.84 

11.36 

1.74 

8.01 

13.59 

8.67 

11.8 

21.53 

10.53 

7.30 

7.14 

1292° 
1150° 

507° 

442° 

less  than  iron, 

1996° 

2016° 

3500° 

617° 

SoO'^ 

less  than  iron 

—39° 

less  than  iron 

tame  as  iron 

greater  than  iron 

1873° 

442° 

773° 

161.8 
419.5 
613.0 
642.5 
558.7 
558.1 

1208.6 
489.4 
709.2 
108.6 
500.0 
848.4 
541.2 
736.6 

1344.0 
657.3 
455.1 
445.7 

12.0 
0.5 
1.5 

*Cadmium 

*Cobalt 

same  as  iron 

*Copper 

13  to  16 

*Gold 

9.1 

*Iron 

29  (maximum) 
0.8  to  1.5 

Lead 

Magnesium 

Manganese 

Mercury 

'^Nickel 

same  as  iron 

♦Palladium 

♦Platinum 

Silver 

18.2 

Tin 

2  to  3.5 

*Zinc 

3.3  to  8.3 

N.  B. — The  star*  refers  to  the  wrought  metal.  Mercury,  tin,  cad- 
mium, bismuth,  lead,  and  zinc,  are  all  fusible  below  red  heat.  Anti- 
mony, just  below  red  heat.  Silver,  copper,  gold,  and  aluminium,  at 
bright  red  heat.  Iron,  cobalt,  manganese,  and  palladium,  at  highest 
forge  heat.  Osmium,  iridium,  platinum,  at  heat  of  oxy-hydrogen 
blowpipe.  Steel  is  to  be  melted  in  a  furnace  of  special  construction, 
called  a  wind  furnace. 


DENTAL   CHEMISTRY. 


Table  No.  10— Tenacity,  Relative  Malleability,  and 
Ductility  of  the  More  Important  Metals. 


Name. 

Tenacity. 

Malleability. 

Ductility. 

Lead 

1.00 

1.20 

1.83 

2.00 

11.50 

12.00 

12.50 

15.00 

18.00 

27.50 

42.00 

6 

4 

7 

(:o) 

1 

2 
5 
3 
8 

10 

Cadmium 

Tin   

9 

Zinc 

8 

Palladium 

6 

Gold 

1 

Silver 

2 

Platinum 

3 

CoDDcr 

6 

Iron 

4 

Steel  

Aluminium 

7 

Explanation:  tenacity,  if  the  weight  required  to  pull 
asunder  a  wire  of  lead  be  taken  as  a  standard  and  called 
I,  the  weight  required  to  pull  asunder  a  wire  of  cadmium 
would  be  a  little  more,  namely  1.2;  that  to  pull  asunder  a 
wire  of  steel,  for  example,  42  times  as  much  as  the  lead. 
Malleability,  if  the  difficulty  with  which  a  mass  of  gold 
can  be  hammered  or  rolled  into  a  thin  sheet,  without 
being  torn,  be  represented  by  i,  iron  will  be  found  to  be 
8  times  as  difficult.  Ductility,  if  the  difficulty  with  which 
gold  can  be  drawn  into  a  wire  be  represented  by  i,  tin, 
for  example,  will  be  drawn  with  9  times  the  difficulty. 
Table  No.  11 — Conducting  Powers  of  Metals. 


Name. 

Heat. 

Electricity. 

Silver 

1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 

1000,  (standard). 
779,  (3d). 
999,  (2d). 

Gold 

Copper 

Aluminium 

Zinc 

290,  (4th). 
168,  (7th). 
123,  (9th). 
180,  (6th). 

83,  (10th). 

46,  (nth). 

12,  (12th). 
184,  (5th). 
131,  (8th). 

Iron 

Tin 

Platinum 

Lead 

Antimony 

Bismuth 

Palladium 

Nickel ;... 

CHEMICAL    PHILOSOPHY.  89 

Explanation:  in  the  table  under  heat,  the  metals  are 
arranged  in  the  order  of  their  conducting  power,  silver 
being  the  best  conductor,  gold  next,  etc.,  etc.  In  the  ta- 
ble under  electricity,  silver  is  taken  as  the  standard,  as  it  is 
the  best  conductor  of  electricity,  and  the  other  metals 
are  compared  with  it,  in  the  pure  state  at  32°  F.  In  some 
works  gold  is  given  3d  place  in  heat-conducting  power, 
copper  2nd. 

Properties  of  metals  and  uses:  mercury  is  useful 
for  amalgaynating  or  dissolving  other  metals;  antimony 
has  the  property  of  hardening  lead  and  tin,  when  melted 
with  them;  bismuth  and  cadmium  make  tin  capable  of 
being  melted  at  lower  temperatures;  nickel  whitens  cop- 
per, and  is  used  in  the  manufacture  of  German  silver. 
Gold,  platinum,  palladium,  silver  are  limited  in  use  by 
their  high  price,  and  the  same  is  true  to  a  certain  extent 
of  aluminium,  although  the  price  of  this  metal  is 
lower  now  than  formerly.  Zinc  has  a  comparatively  high 
degree  of  expansibility;  gold  is  the  most  malleable  of 
metals  as  also  the  most  ductile;  silver  is  the  best  con- 
ductor of  heat  and  electricity;  the  tenacity  of  metals  is 
usually  diminished  by  heating;  malleability  and  ductility 
are  developed  in  some  metals  by  heating,  but  impaired 
by  carrying  heat  too  far;  in  alloys,  heating  impairs  tenac- 
ity, malleability,  and  ductility;  crystalline  metals,  as  bis- 
muth, lack  malleability,  etc.;  metals  may  be  obtained  in 
crystalline  form  by  electrolysis,  either  by  introducing 
other  metals  in  strips  or  rods  into  their  solutions,  as  a  rod 
of  zinc  into  a  solution  of  a  lead  salt,  or  by  passage  of  a 
weak  electric  current  through  their  solutions.  Gold  may 
be  obtained  in  crystalline  form  by  introduction  of  a  stick 
of  phosphorus  into  a  solution  of  one  of  its  salts. 

158.  General  properties  of  alloys  of  the 
metallic  elements. — Alloy  is  the  name  g:iven 


DENTAL   CHEMISTRY. 


90 

to  a  combination  obtained  by  fusing  metals  to- 
gether. Alloys  are,  as  a  rule,  chemical  com- 
pounds dissolved  in  excess  of  one  of  the 
constituent  metals,  but  many  are  merely  me- 
chanical mixtures,  or  niolecidar  mixtures,  as 
the  term  is.  All  alloys  exhibit  the  metallic  na- 
ture in  their  physical  characteristics. 

As  regards  specific  gravity,  an  alloy  of  gold  and  silver 
is  lighter  than  the  theoretical  mean  of  its  constituents; 
brass,  and  an  alloy  of  lead  and  tin,  heavier;  in  other 
words,  the  gold  and  silver  alloy  is  formed  by  expansion, 
the  latter  by  contraction.  In  the  formation  of  some  al- 
loys there  is  no  change  in  volume.  In  color,  alloys  are 
usually  gray,  unless  there  is  sufficient  copper  or  gold  to 
impart  the  characteristic  color  of  those  metals.  Alloys 
are  usually  harder  and  more  brittle,  less  ductile  and 
less  tenacious,  than  the  constituent  metal  exhibiting 
these  qualities  in  the  highest  degree;  aluminium  bronze  is 
an  exception,  its  tenacity  being  greater  than  that  of  either 
of  the  constituent  metals. 

The  fusibility  of  an  alloy  is  generally  greater,  i.  e.,  the 
alloy  melts  more  readily  than  that  of  the  least  fusible 
constituent  metal  and  sometimes  than  that  of  any  con- 
stituent metal.*  An  alloy  heated  gradually  to  near  its 
fusing  point  undergoes  a  change;  its  constituents  reunite 
to  form  a  mass  now  fusible;  if  the  fluid  be  poured  off,  a 
solid  alloy  is  obtained  less  fusible  than  the  original.  In 
this  way  copper  is  separated  from  silver.  An  alloy  of 
zinc  or  of  mercury  is  decomposed  by  heat,  but  at  a  higher 
temperature  than  the  point  of  ebullition  of  the  metal.  As 
regards  temperature,  an  alloy  of  94  copper  to  6  tin,  if  slow- 
ly cooled,  becomes  brittle,  but,  if  cooled  rapidly  with  cold 

♦Thus,  tin  unites  with  gold  far  below  the  melting  point  of  gold. 


CHEMICAL   PHILOSOPHY.  q-. 

water,  malleable.  Mercury,  bismuth,  tin,  and  cadmium 
give  fusibility  to  alloys,  tin  hardness  and  tenacity,  lead 
and  iron  hardness,  antimony  and  arsenic  brittleness. 
Metals  are  usually  fused  under  a  layer  of  charcoal  to  pre- 
vent oxidation;  they  are  mixed  by  agitation  and  allowed 
to  cool  slowly. 

Certain  peculiarities  of  alloys  as  to  solubility  must  be 
noticed:  platinum  is  insoluble  in  nitric  acid,  but  an  alloy 
of  platinum  with  silver  or  gold  is  soluble  in  the  acid.  Sil- 
ver is  readily  soluble  in  nitric  acid,  but  an  alloy  of  silver 
with  25  per  cent,  gold  is  insoluble. 

The  affinity  of  an  alloy  for  oxygen  is  greater  than  that 
of  the  separate  metals,  but  the  action  of  air  is  in  general 
less  on  alloys  than  on  the  separate  metals  composing 
them,  with  some  exceptions. 

Some  difficulty  is  occasionally  experienced  in  obtaining 
a  perfectly  uniform  alloy,  on  account  of  the  different 
specific  gravities  of  the  metals  composing  it — each  metal 
assuming  the  level  due  to  its  specific  gravity.  This  result 
is  not  so  likely  to  occur,  when  the  metals  employed  are 
in  small  quantities,  briskly  stirred,  and  suddenly  cooled. 
In  alloying  three  or  more  metals  differing  greatly  in  fusi- 
bility, or  that  have  but  little  affinity  for  one  another,  it  is 
better  to  unite  first  those  that  most  readily  combine,  and 
then  this  combination  with  the  remaining  metal  or  met- 
als. If,  for  example,  it  is  desired  to  unite  a  small  quan- 
tity of  lead  with  brass  or  bronze,  some  difficulty  would  be 
experienced  in  forming  the  alloy  by  direct  incorporation 
of  the  metals,  but  union  could  be  readily  effected  by  first 
melting  the  lead  with  zinc  or  tin,  and  then  adding  the 
melted  copper. 

Alloys  consisting  of  two  metals,  one  readily  oxidiza- 
bie,  the  other  possessing  less  affinity  for  oxygen,  may  1)6 
readily  decomposed  by  the  combined  action  of  heat  and 
air. 


92 


DENTAL   CHEMISTRY. 


159.  Solders:  it  is  often  necessary  to  unite 
several  pieces  of  the  same  metal,  or  of  differ- 
ent metals.  For  such  work  a  kind  of  alloy- 
called  solder  is  used.  Solders  usually  contain 
the  metal  on  which  they  are  to  be  used,  to- 
gether with  some  other  metal  or  metals,  which 
shall  reduce  the  fusing-  point  without  affecting 
the  color. 

[A  solder  suitable  for  use  in  prosthetic  dentistry  should 
fuse  at  a  much  lower  temperature  than  the  plate  upon 
which  it  is  to  be  used.  Its  color  should  be  as  nearly  as 
possible  the  same,  and  it  should  withstand  the  action  of 
the  fluids  of  the  mouth  nearly  as  well.  These  properties 
may  be  obtained  by  the  addition  of  small  amounts  of  sil- 
ver, copper,  or  brass.     (Essig.)]. 

Solders  have  been  divided  into  two  classes:  i^d)  solders 
made  by  the  fusion  of  the  metal  itself,  without  others,  and 
(^)  solders  made  on  a  metal  with  another  metal;  or  by  an 
alloy  applied  to  the  surfaces  which  are  to  be  united.  In 
the  last  case  the  metal  or  alloy  must  be  more  fusible  than 
the  metal  to  be  soldered,  and  have  a  more  powerful 
chemical  affinity  for  it. 

Hard  solder  is  used  for  metals  difficult  to  melt,  soft  sol- 
der for  those  not  so  difficult. 

160.  General  properties  of  the  non-metallic  ele- 
ments.— It  is  difficult  to  draw  a  sharp  line  between  met- 
als and  metalloids,  but  as  a  general  rule  those  that  are 
not  gaseous  at  ordinary  temperatures  have  no  metallic 
lustre,  are  of  low  specific  gravity,  neither  malleable  nor 
ductile,  conduct  heat  and  electricity  very  imperfectly. 
The  nitrogen  group,  N,  P,  As,  Sb,  and  Bi  is  remarkable  for 
a  change  from  non-metallic  properties  to  metallic  as  the 
atomic  weight  increases,  beginning  with  nitrogen,  atomic 
weight  14  and  gaseous,  and   ending  with  bismuth,  210, 


CHEMICAL  PHILOSOPHY.  93 

which  has  well-marked  metallic  properties.  Arsenic  is  a 
metalloid  with  strongly  metallic  characteristics,  uniting 
with  chlorine  like  a  basic  metal,  but  on  the  other  hand 
uniting  with  oxygen  to  form  anhydrides. 

i6i.  Classification  according  to  valence. — Owing  to 
the  didactic  character  of  this  book  those  elements  of  im- 
portance to  the  dentist  will  be  studied  in  such  a  way  as  to 
keep  their  valence  and  electro-chemical  relations  constantly 
in  view.*  Table  i  of  Professor  Seamanf  will  be  taken  as 
a  basis  for  the  classification. 

♦Those  interested  in  the  further  study  of  theoretical  chemistry 
should  procure  Lothar  Meyer's  "Modern  Theories  of  Chemistry" 
translated  by  Bedson  and  Williams. 

fProfessor  Seaman  divides,  for  didactic  purposes,  the  elements  as 
follows: 

A.  Gases:  O,  H,  N,  CI,  F. 

B.  Halogens:  I,  Br,  CI. 

C.  Metals:  As,  Sb,  Fe,  etc. 

[Sub-classes  of  metals:  metals  of  the  alkalies,  Na,  K,  Li;  metals 
of  the  alkaline  earths,  Ba,  Ca,  Sr,  Mg;  metals  proper,  as  Fe,  Pb,  Sn.]. 

D.  Metalloids:  as  C,  P,  Si,  S. 

Witthaus's  classification  is  excellent  in  many  respects:  Class  I, 
typical  elements:  H  and  O.  Class  II,  elements  whose  oxides  plus 
water  form  acids,  viz:  Fl,  CI,  Br,  I,  S,  N,  P,  As,  etc.  Class  III:  ele- 
ments whose  oxides  plus  water  in  some  form  bases,  in  others  acids: 
Au,  Cr,  Mn,  Fe,  Al,  Pb,  Bi,  etc.  Class  IV,  elements  whose  oxides 
plus  water  form  bases  only:  Li,  Na,  K,  Cu,  Mg,  Zn,  etc. 


u 


DENTAL  CHEMISTRY. 


CHAPTER  III. 


Inorganic  Chemistry.    The  Elements  and  Their 
Inorganic  Compounds. 

Monads.— The  elements  will  be  taken  up  in  the  order 
of  their  valence,  monads  first.  Of  monads  those  positive* 
to  hydrogen  will  be  treated  first,  then  those  negative  to 
it. 

Table  12.    Monads. 


Potassium 
Sodium 
[Ammonium] 
Lithium 
Silver 
Hydrogen 
Iodine 
Bromine 
Chlorine 
Fluorine. 


J 


Monads  positive 
to  hydrogen. 


Monads  negative 
to  hydrogen. 


Hydrogen  forms  Hydrides  with  those  elements  positive 
to  itself,  as  KH,  potassium  hydride.  Combined  with 
those   negative   to   it  iodides,   bromides,    chlorides,   and 

♦See  Table  1.  The  student  will  do  well  to  study  the  properties  of 
hydrogen  (section  176)  and  of  oxygen  (section  241)  before  beginning 
this  chapter. 


INORGANIC   CHEMISTRY  95 

fluorides  are  formed.  Moreover,  all  in  the  list  above  hy- 
drogen are  positive  to  all  in  the  list  below  hydrogen.  The 
elements  positive  to  hydrogen  in  this  list  are  all  metals, 
those  negative,  non-metals. 

Potassium: — Symbol:  K.  Latin  name:  Kalium.  Equiv- 
alence: I.  Specific  gravity :  0.86.  Atomic  weight  {2,f^'^xoyi.\. 
39.  Revised  atomic  weight:  39.0196.  Electrical  state :  -\-. 
Fusing  point:     I44°F. 

Brilliant,  white  metal,  with  high  degree  of  lustre,  soft, 
floats  on  water  and  takes  fire  spontaneously  when  thrown 
on  it,  yielding  an  alkaline  solution. 

162.    Potassium  compounds. 

Table  13 — Some  Compounds  of  Potassium. 

Name,  Formulae.  Uses,  etc. 

White,   soluble   in  water 
(6  in    100).      Used    in 

rhlnratp  KCIO  mouth  washes  and  g-ar- 
cniorate        KUIU3       ^^^     j^^  j^^.^^  ^^^^^  j^ 

poisonous.  Sparingly 
soluble  in  alcohol. 

Antacid,  used  in   mouth 

washes.  In  larg"e  doses 

Bicarbonate  KHCO3    is     corrosive      poison. 

Soluble  in  water,  insol- 
uble in  alcohol. 

White,  soluble    crystals. 
Given  internally  in  con- 
Bromide        KBr  vulsions,  etc.,  and  used 

locally  to  diminish  sen- 
sibility before  taking 
impressions. 


96 


DENTAL   CHEMISTRY 


Table  13. — Continued 

Transparent,       colorless 
solid,  soluble  in  water. 

Chloride        KCl  Found  in  the   body  in 

fluids,  blood  corpuscles, 
and  in  muscle  juice. 
Made  by  dissolving 
iodine  in  potassium  hy- 
drate. Larg^e,  white 
Iodide  KI  translucent,  cubical  cry- 

stals of  a  saline  taste. 
Readily  soluble  in  water. 
Solutionsdissolve  iodine. 
163.    Potassium  hydrate.— 
Synonyms:  Potassa  U.  S.  P.,  Potassa  Caus- 
tica  (Br.  P.),  caustic  potash. 

Theoretical  constitution:  KHO  or  KOH,  the 
hydrate  (hydroxide)  of  potassium.  Molecular 
weight,  56. 

Preparation:  by  boiling-  potassium  carbon- 
ate with  slacked  lime  (calcium  hydrate): 
K2CO3  +  Ca(H0)2  =  CaCOa  +  2KHO. 
Properties:  the  impure  contains  lime  and  is 
called  potash  by  lime:  purified  by  dissolving 
in  alcohol  and  evaporating  to  dryness,  re- 
melted,  and  cast  in  sticks  it  is  known  as  potash 
by  alcohol.  White,  opaque  sticks  or  lumps, 
alkaline,  readily  soluble  in  water,  caustic, 
escharotic,  and  corrosive  poison. 

Potassa  cum  cake:  equal  parts  KHO  and 
CaO,  grayish-white  powder,  milder,  and  less 


INORGANIC   CHEMISTRY.  Q^ 

deliquescent;  in  a  paste  called  Vienna  paste, 
used  in  dentistry. 

Robin  soil  s  remedy  contains  potassium  hy- 
drate and  carbolic  acid,  equal  parts. 

Liquor  potassce  is  a  5  per  cent  solution  of 
potassium  hydrate  in  water. 

Toxicology:  potassium  hydrate  is  a  corrosive  poison 
and  its  action  on  tissues  is  very  violent  and  penetrating. 
Forty  grains  have  caused  death.  In  the  treatment  the 
stomach  pump  must  7iot  be  used,  dilute  vinegar  should  at 
once  be  given,  lemon  juice,  orange  juice,  olive  oil,  and 
milk  freely.  Stimulants  are  indicated  if  there  is  much 
pain.  Solutions  of  potassium  hydrate  or  carbonate  have 
a  soapy  "feel"  and  are  alkaline  in  reaction.  Burns  from 
the  agent  should  be  treated  with  dilute  vinegar  and  then 
with  oil. 

164.    Potassium  Nitrate. — 

Synonyms:  nitre,  saltpetre,  Sal  Prunella. 
Official  name,  Potassii  Nitras. 

Theoretical  constitution:  KNO3,  i  atom  of 
potassium,  i  of  nitrogen,  and  3  of  oxygen  to 
the  molecule.     Molecular  weight,  loi. 

Preparation:  made  from  crude  sodium 
nitrate  by  double  decomposition  with  potas- 
sium chloride. 

Properties:  colorless  crystals,  anhydrous, 
very  soluble  in  hot  water,  readily  soluble  in 
cold,  nearly  insoluble  in  alcohol,  permanent  in 
dry  air,  neutral,  odorless. 

Uses  in  dentistry:  locally  and  in  mouth 
washes  as  an  antiseptic  and  refrigerant.  In 
refining  gold,  when  it  is  used  as  an  oxidizing 


93  DENTAL  CHEMISTRY. 

ag-ent  for  metals  alloyed  with  gold.     Roasting- 
an  alloy  with  nitre  will  often  set  the  g:old  free. 

Toxicology:  potassium  nitrate  is  poisonous,  causing 
severe  burning,  abdominal  pains,  nausea,  vomiting  of 
blood,  great  prostration,  tremors,  collapse.  One  ounce 
has  proved  fatal.  The  treatment  is  to  give  an  emetic, 
mucilaginous  and  demulcent  drinks,  and  stimulants. 

165.  Potassium  Permanganate. — 

Synonyms:  permanganate  of  potash.  Official  name, 
Potassii  Permanganas. 

Theoretical  constitution:  KgMnaOs  or  KMnO^,  derived 
from  permanganic  acid.  Permanganic  acid,  HzMngOg, 
may  be  deemed  to  be  derived  from  manganese  heptoxide 
(MniO?)  plus  water  (HoO);  potassium  permanganate 
K2Mn20g,  by  exchanging  the  two  atoms  of  hydrogen  in 
the  acid  for  two  of  potassium.      Molecular  weight,  313.8. 

Properties  and  dental  uses:  potassium  per- 
mang-anate  occurs  in  the  form  of  dark  purple 
crystals  which  impart  a  fine,  deep,  purple  color 
to  water  even  when  in  very  minute  propor- 
tions. It  is  a  deodorizer,  disinfectant,  and,  in 
concentrated  solution,  a  caustic. 

Co7idys  Fluid  contains  32  g-rains  of  it  to  the 
pint  of  distilled  water. 

Liquor  Potassii  Permanganatis  contains  64 
grains  to  the  pint  of  distilled  water. 

In  dental  practice  the  permang:anate  is  used 
locally  as  a  deodorizer,  disinfectant,  and  an- 
tiseptic. 

166.  Sodium: — 

Symbol:  Na.  Latin  name:  Natrium  or  Natron. 
Equivalence-.  I.  Specific  Gravity. — 0.97.  Atomic  zveight 
(approx.):  23.     Revised  atomic  weight: — 22.998.     Electrical 


INORGANIC    CHEMISTRY. 


99 


state: — X.      Fusing  point: —  2c6.°6  F.       Properties: — Soft, 
white,  readily  oxidized  metal, 

167.    Sodium  Compounds.— 

Sodium  Hydro-Carbonate  or  Bicarbonate. 

Synonyms:  bicarbonate  of  sodium,  bicar- 
bonate of  soda,  sodium  acid  carbonate,  sesqui- 
carbonate  of  sodium,  "baking-  soda." 

Theoretical  constitution:  sodium  hydrocar- 
bonate,  NaHCOa,  is  what  is  called  an  acid 
salt,  because  all  the  hydrogen  atoms  of  the 
acid  from  which  it  is  derived  have  not  been 
replaced  by  the  positive  atom.  The  term  acid 
salt  should  not  confuse  the  beginner  as  to  the 
reactio7i  of  the  substance  to  litmus  paper, 
which  has  nothing  to  do  with  the  theoretical 
name. 

Sodium  bicarbonate  is  composed  of  one 
atom  of  sodium,  one  of  hydrogen,  one  of  car- 
bon, and  three  of  oxygen.  By  weight  23  of 
sodium,  I  of  hydrogen,  12  of  carbon,  48  of  oxy- 
g-en;  molecular  weight,  84. 

Preparation:  made  by  passing  carbon  diox- 
ide over  sodium  carbonate  from  which  the 
larger  portion  of  water  of  crystallization  has 
been  expelled: 

Na^COa  +  H2O  +  CO2  =  2NaHC03. 

Sodium  water  carbon  sodium 

carbonate  dioxide  bicarbonate. 

The  sodium  carbonate  used  is,  as  will  thus 
readily  be  seen,  an  entirely  different  substance 
from  the  bicarbonate.    The  former  is  known 


100 


DENTAL  CHEMISTRY. 


in  commerce  as  "sal  soda,"  and  familiarly 
known  as  "washing-  soda." 

Properties:  sodium  bicarbonate  is  a  white 
powder,  having-  a  mildly  saline,  cooling-  taste, 
a  slightly  alkaline  reaction,  is  soluble  in  12 
parts  of  water,  insoluble  in  alcohol;  8  parts  of 
the  bicarbonate  are  soluble  in  100  of  g"lycerine 
(by  weight).  Its  solutions  are  nearly  neutral 
to  litmus  paper. 

Use  in  dentistry:  sodium  bicarbonate  is  in 
particular  used  as  an  antacid  ingredient  of 
dentifrices,  and  its  uses,  in  g-eneral,  in  dental 
practice  are  in  consequence  of  its  antacid  prop- 
erties. 

168.  Various  sodium  compounds:  all  are  soluble  in 
water  to  a  greater  or  less  degree  and  most  of  them  in 
solution  turn  red  litmus  blue.  Many  of  them  are  white  or 
colorless. 


Table  14 — Sodium  Compounds. 


Name. 
Chloride 

Sulphite 

Sulphate 
Carbonate 
Arseniate 

Hydrate 


Phosphates 


Formulae. 
NaCl 

Na2S03 

Naz  SO4 

Na2CO3,10H2O 

NazHAsOi,  7H2O 

KHO 

NasPOi 
'        NazHPOi 
!         NaHzPO^ 


Origin,  Uses,  etc. 

Common  salt  is  found  in  every 

fluid  and  organ  of  the  body. 

(  Antiseptic,  disinfectant,  and  de- 

j    odorizer.      Used  in   bleaching 

(   teeth  with  boracic  acid. 

Glauber's  salt. 
Washing  Soda. 
Poisonous,  colorless,  efflorescent. 

(  Caustic  soda.  Comes  in  form  of 
(    sticks.     Readily  soluble. 
<  Basic  phosphate,  alkaline,  and 
/    purgative. 

Neutral  phosphate.     Found  in 
the  tissues. 

Acid  phosphate  of  sodium. 


INORGANIC   CHEMISTRY, 


101 


169.  Sodium  Borate  or  Borax. — 

Synonyms:  sodium  biborate,  sodium  tetra- 
borate, Sodii  Boras  (U.S.P),  Sodae  Boras 
(B.P.). 

Theoretical  constitution:  formula  Na2B407, 
explained  by  regarding;  it  as  NaaO^ 6203)2  or 
Na20.2B203.  Boric  oxide  (anhydride)  B2O3, 
has  the  property  of  uniting  directly  with  oxides 
of  the  positive  elements  sodium,  potassium, 
etc.  Borax  is  not,  therefore,  derived  from 
boracic  acid  but  formed  by  the  direct  combin- 
ation of  sodium  oxide,  NaoO,  with  boric  ox- 
ide or  anhydride,  B2O3.  The  molecule  of 
sodium  oxide  combines  with  two  molecules  of 
boric  oxide,  forming  Na20.2B203.  Borax  con- 
tains also  ten  molecules  of  water  of  crystalliza- 
tion, so  that  the  full  formula  is  Na20.2B203  + 
10H2O. 

Properties  and  uses  in  dentistry:  borax  is  a 
white,  soluble,  efflorescent  substance  which 
melts  at  a  low  heat,  swells  greatly,  at  a  higher 
temperature  becomes  a  clear  liquid,  then  a 
vitreous  substance  (borax  glass).  It  is  Useful 
in  blow  pipe  analysis,  as  by  the  "borax  bead" 
method;  as  a  flux  for  melting  metals;  in  sold- 
ering metals;  in  solution,  for  hardening  plaster 
casts;  as  a  local  application,  etc.,  etc- 

170,  Sodium  Hypoclilorite. — 

Theoretical  constitution:  NaClO,  one  atom  of  sodium, 
one  of  chlorine  and  one  of  oxygen  in  its  molecule.     This 


102  DENTAL    CHEMISTRY. 

substance  is  only  indirectly  of  interest  as  one  of  the  in- 
gredients of  the  chlorinated  soda  solution. 

Liquor  SodcB  Chlorates : 

Synonyms:  Labarraque's  solution,  solution  of  chloride 
of  soda;  chlorinated  soda  solution. 

Preparation:  made  by  decomposing  a  solution  of  chlor- 
inated lime  with  one  of  sodium  carbonate: 

[Ca(C10)2  +  CaCliJ  +  2NaC03  =   [2NaC10  +  2NaCl]  +    2CaC03 
Chlorinated  lime.  Clilorinated  soda.  Calcium 

carbonate. 

Properties:  clear,  pale  liquid,  slightly  greenish  yellow 
in  color,  of  faint  chlorine  odor,  alkaline  taste  and  reaction. 
Sp.  gr.,  1.044.  Powerful  disinfectant,  deodorizer,  antisep- 
tic, bleaching  agent. 

Use  in  dentistry:  used  locally  for  its  antiseptic  proper- 
ties and,  in  combination  with  powdered  alum,  as  a  bleach- 
ing agent  for  discolored  teeth.  It  slowly  decomposes  on 
exposure  to  air  and  light,  and  should  be  kept  in  a  dark 
place  in  a  bottle  provided  with  a  glass  stopper.  It  is 
advisable  to  keep  soda  and  potash  solutions  in  bottles 
whose  glass  stoppers  have  been  dipped  in  paraffine. 

Eau  de  Javelle  contdans  potassiiwi  hypochlorite. 

171.    Ammonium  and  its  Compounds.— 

Ammonium  (NH4)  is  what  is  known  as  a 
radical.  (See  Org-anic  Chemistry).  It  is  not 
positively  known  to  exist  nor  is  its  oxide. 
There  are  reasonable  grounds,  how^ever,  for 
supposing-  that  it  does  actually  exist  in  cer- 
tain compounds  called  the  ammonium  com- 
pounds, all  of  which  contain  NH4  in  their  for- 
mulae. Ammoni//;//  is  not^ammon/^'/  the  latter 
is  a  well-known  gas,  NH3,  while  ammonium 
has  never  been  isolated  and  has,  therefore,  only 
a  hypothetical  existence.    Ammonium  would 


INORGANIC   CHEMISTRY. 


103 


seem  in  the  main  to  resemble  sodium  and 
potassium;  there  are,  however,  points  of  dis- 
similarity. 


Names. 

Hydrate, 

(Ammonia 
water). 


Table  15.     Compounds  of  Ammonium 

Formulae. 
H4NHO  or  NH4HO 


Sometimes  written 
AmHO.  May  be 
deemed  a  hydrate 
of  the  radical  am- 
monium. 


(NH4HCO3,  NH4NH2CO2) 

Really  a    mixture    of 

the   acid  carbonate 

and  the  carbamate. 

Molecular  wt.,  157. 

NHiCl=  63.4 


Properties. 

Volatile,  caustic  liquid  of  power- 
ful odor.  Aqua  Ammonias  is  a 
solution  of  ammonia  gas  in 
water,  of  sp.  gr.  0.959.  Aqua 
Ammoniae  Fortior  contains  28 
per  cent,  of  the  gas  and  is  of 
sp.  gr.  0.900;  it  is  a  powerfully 
corrosive  poison. 

Has  strong  odor  of  ammonia  and 
is  freely  soluble  in  water. 
Loses  CO2  and  NH3  on  expos- 
ure to  the  air. 


White,  crystalline  powder;  very 
easily  soluble  in  water,  but  not 
hygroscopic.  Used  as  flux  in 
refining  gold,  etc.,  and  locally. 


Carbonate, 

Ammonii 
carbonas. 
Hartshorn 

salt. 
Sal  Volatile. 

Chloride, 

or  muriate. 

Sal 
ammoniac. 

Lithium : — 

Symbol:     Li. 
Specific  gravity 
zvt.     (revised): 
point:     356°  F.  Properties: 
the  lightest  metal  known. 

172.    Silver.— 

Symbol:  Ag.  Latiji  Jiame:  Argentum.  Equivalence: 
I  and  III.  Specific  gravity:  10.40  to  10.57.  Atomic 
ivcight  iq8.  Revised  atomic  zveight:  107.675.  Electrical 
state :  +.  Fusing  point:  i873*'F.  Expands  on  solidifying. 
Le7tgth  of  bar  2Lt  212:  1.0021;  (6th  rank).  Wt.  of  cubic  ft. 
in  lbs.:  657.3.  Tensile  strengtJi :  18.2;  (lead=  1).  Teiiacity : 
12.5*;  (5th  rank).  Malleability:  2;  (2d  rank).  Ductility: 
2;  (2d  rank).  Conducting  power,  heat:  i;  (ist  rank). 
Conducting  power,   electricity:     i;    (ist    rank).     Resistance 


Latin  name:  Lithium.  Equivalence :  \. 
0.59.  Atomic  wt.  (approx.)  :  7.  Atomic 
7.0073.  Electrical  State:  +•  Fusing 
White,  oxidizable  metal  and 


^Compared  with  lead. 


104  DENTAL   CHEMISTRY 

to  air,  etc,;  tarnished  by  sulphuretted  hydrogen,  but  not 
affected  by  air.  Solubility:  in  nitric  acid,  hot  strong  sul- 
phuric, hydrochloric  with  difficulty;  not  attacked  by 
caustic  alkalies  nor  by  melted  nitre.  It  is  dissolved  by 
mercury.  Direct  combinations:  with  halogens,  chlorine, 
bromine,  etc.,  and  with  sulphur  and  phosphorus.  Color 
white,  brilliant.  Structure :  isometric  crystals,  when  cooled 
slowly  from  fusion.  Consistence:  soft.  Intermediate  in 
hardness  between  gold  and  copper.  Compounds :  argentic, 
as  argentic  nitrate,  etc.  Ordinary  alloys:  silver  coins, 
gold  solders,  silver  solders,  silver  vessels,   silver   jewelry. 

Occurrence:  silver  is  found  in  combination 
with  some  of  the  halogens  as  chlorine,  bro- 
mine, iodine,  with  various  other  non-metals  as 
sulphur,  arsenic,  antimony,  and  with  copper. 
It  occurs  in  the  Western  states,  in  Mexico, 
Saxony,  Hungary,  Norway,  South  America 
and  elsewhere.  It  is  sometimes  found 
native^. 

Preparation:  the  methods  are  various  and 
elaborate.  The  Washoe  process  is  to  grind  the 
ores  with  water,  in  iron  pans  heated  by  steam. 
Mercury  is  added,  the  sulphide  of  silver  is 
decomposed  by  the  iron,  sulphide  of  iron 
formed  and  metallic  silver  set  free,  dissolved 
in  mercury  and  the  mercury  separated  by 
pressure  and  distillation. 

♦Native  silver  is  that  found  not  as  a  sulphide,  etc.,  but  uncombined. 
Native  silver  is  found  in  crystals,  threads,  or  amorphous  masses, 
weighing  often  several  pounds.  It  is  associated,  nearly  always,  with 
other  metals  in  small  quantities,  and  accompanied  by  its  sulphide  or 
chloride. 


INORGANIC   CHEMISTRY.  1Q5 

Pure  silver  may  be  prepared  by  reducing  the 
chloride,  by  fusing  it  with  dry  sodium  car- 
bonate. Other  methods  are  also  used:  one  is 
to  dissolve  standard  or  other  grades  of  silver  in 
slightly  diluted  nitric  acid,  precipitate  the 
solution  by  excess  of  common  salt,  place  the 
well-washed  chloride  in  water  acidulated  with 
hydrochloric  acid,  and  add  a  few  pieces  of 
clean  wrought  iron:  hydrogen  is  evolved 
which,  uniting  with  the  chlorine  of  silver  chlor- 
ide, leaves  the  silver  as  a  spongy  mass.  After 
the  removal  of  the  iron  and  decantation  of 
the  liquid,  the  silver  is  well  washed  in  hot 
water  containing  a  little  hydrochloric  acid, 
dried  and  melted. 

Uses  in  dentistry:  silver  is  used  in  amalgam 
alloys  and,  according  to  Flagg,  is  the  first, 
most  important,  and  essential  metal  of  a 
good  amalgam  alloy  for  filling  teeth;  it  is  the 
largest  component  of  every  truly  good  "sub- 
marine," "usual,"  or  "contour"  alloy  in  the 
market.  Its  presence  in  an  amalgam  is  es- 
sential to  proper  setting;  it  notably  maintains 
the  bulk  integrity  of  the  filling;  though  dis- 
colored by  sulphuretted  hydrogen,  the  silver 
sulphide  formed  is  highly  conducive  to  the 
permanent  saving  of  teeth  largely  decayed 
and  predisposed  to  continued  decay.  Silver 
has  also  been  used  in  dental  plates. 


No.  3. 

Silver,  5^  dwts. 
Brass  wire,  40  grains. 


106    .  DENTAL    CHEMISTRY. 

173.  Silyer  alloys  and  alloys  resembling  silver. — 

Silver  coinage:  silver  90,  copper    10.     Silver  vessels: 

silver  95,  copper  5.     Silver  jewelry:  silver  80,    copper  20, 

An  alloy  used  in  England  for  temporary  dentures  is 

silver  24  parts,  platinum  3  to  10  parts. 

Gemtan  silver  con\.2dns  no  silver,  but  is  an  alloy  of  cop- 
per, nickel,  and  zinc,  in  the  proportions  of  40.4  copper, 
31.6  nickel,  25.4  zinc,  and  sometimes  2.6  iron. 

174.  Silver  solder  \s  32.3  parts  copper,  38.5  silver,  29.2 
zinc.     Others  are  as  follows:  (Richardson). 

No.  1.  No.  2. 

Silver,  66  parts.  Silver,  6  dwts. 

Copper,  30  parts.  Copper,  2  dwts. 

Zinc,  10  parts.  Brass,  1  dwt. 

When  the  plate  to  be  united  consists  of  pure  silver 
alloyed  with  platinum,  the  solder  may  be  formed  of  the 
standard  metal  (coin),  with  jolh  to  ek  its  weight  of  zinc, 
according  to  the  amount  of  platinum  in  the  alloy. 

175.    Compounds  of  silver. 

Silver  Nitrate  or  Argentic  If itrate.— 

Synonyms:  lunar  caustic,  lapis  infernalis. 
Official  name,  Argenti  Nitras. 

Theoretical  constitution:  AgNOg,  one  atom 
of  silver,  one  of  nitrogen,  three  of  oxygen;  by 
weight,  silver  107.7  parts,  nitrogen  14,  oxygen 
48.     Molecular  weight,  169.7. 

Properties  and  uses:  on  evaporating  a  solu- 
tion of  silver  in  nitric  acid  and  water,  nitrate 
of  silver  is  obtained  in  the  form  of  colorless, 
heavy,  shining,  rhombic  plates.  It  is  black- 
ened by  exposure  to  light,  and  by  contact  with 
organic  matter.  It  is  also  prepared  in  stick 
form,  by  fusing  and  pouring  into  moulds.    It 


INORGANIC   CHEMISTRY.  107 

is  very  soluble  in  water,  and  slightly  in  alcohol. 
It  is  used  in  dentistry  as  an  astringent,  styptic, 
and  obtunding  agent.  It  blackens  tissues  with 
which  it  comes  in  contact,  and  is  a  powerful 
escharotic.  Should  be  kept  in  amber  bottle 
with  glass  stopper. 

Toxicology:  silver  nitrate  is  an  irritant,  corrosive 
poison.  The  antidote  is  common  salt  or  sal-ammoniac. 
Emetics  should  be  given,  and  white  of  egg  adminis- 
tered freely. 

Silver  Sulphide.— Silver  has  a  strong  affinity  for  sul- 
phur, the  sulphide,  Ag2S,  being  formed  in  the  mouth  by 
action  of  sulphuretted  hydrogen  on  an  alloy  containing 
silver.  Silver  can,  therefore,  not  be  used  in  connection 
with  substances  containing  sulphur,  as  rubbers.  Silver 
sulphide  is  soluble  in  nitric  acid,  is  soft  and  malleable. 

Silver  Chloride,  AgCl,  is  formed  when  either  common 
salt  or  hydrochloric  acid  is  added  to  a  solution  of  silver 
nitrate. 

Silver  Oxide,  AgjO,  is  obtained  as  a  brown  precipitate, 
when  solution  of  silver  nitrate  is  decomposed  by  potash. 
Take  of  silver  nitrate  lOO  Gm.,  of  distilled  water  200  C.c, 
of  solution  of  potassa  (official)  6oo  C.c.  Dissolve  the  sil- 
ver nitrate  in  water  and  add  solution  of  potassa  as  long  as 
any  precipitate  is  produced  by  it.  Wash  the  precipitate 
with  distilled  water,  until  washings  are  nearly  tasteless. 
Dry  the  product  and  keep  it  well  protected  from  the 
light. 

It  parts  with  its  oxygen  easily  and  must  not  be  heated 
nor  brought  into  contact  with  ammonia.  Should  be 
kept  in  a  well-closed  bottle  and  in  a  cool  place.  It  is 
used  as  a  coloring  matter  for  artificial  teeth. 

176.    Hydrogen.— 

Symbol:    H.    Atoms  in  viokcnle:    H2.   Atomic  weight'.  \, 


108  DENTAL  CHEMISTRY. 

Molecular  weight'.  2.  De7isity\  i.  Specific  gravity.  0.0692. 
WeigJit  of  one  litre  of  hydrogen  gas:  0.0896  gramme. 
How  liquified',  by  pressure  of  650  atmospheres  at — 140°  C. 

Occurrence  in  Nature. — In  volcanic  gases  and  sun's 
atmosphere. 

How  made. — By  decomposing  an  acid  with  a  metal: 
thus,  sulphuric  acid  with  zinc:  HgSOt  +  Zn  =  ZnSOi 
+     H,. 

Properties. — Has  affinity  for  chlorine  only;  at  higher 
temperatures  for  oxygen.  Is  a  gas,  colorless,  tasteless, 
odorless,  transparent,  and  but  slightly  soluble  in  water. 
Is  the  lightest  known  substance  and  burns  with  the  hot- 
test flame. 

Use  in  dentistry. — Used  in  connection  with  oxygen  in 
the  oxyhydrogen  blow  pipe  for  fusing  refractory  substances. 
(See  Oxygen).  In  combination  with  carbon  alone  forms 
hydrocarbons,  among  which  are  the  volatile  oils,  as  oil  of 
cloves.     (See  Organic  Chemistry). 

177.  Compounds  of  hydrogen:  hydrogen 
monoxide  or  water. — 

Synonyms:  Aqua;  distilled  water,  Aqua 
Destillata.  Theoretical  constitution:  H2O, 
hydrog"en  monoxide,  composed  of  two  atoms 
of  hydrogen  and  one  of  oxygen,  by  weight  8 
parts  of  oxygen  to  i  of  hydrogen.  Molecular 
weight,  18.     Specific  gravity,  i. 

Origin:  occurs  in  nature  in  lakes,  rivers,  etc., 
and  in  three  states  the  solid  as  ice,  the  liquid, 
and  the  gaseous  as  steam  or  vapor.  In  the  air 
it  is  in  form  of  vapor.  Seven-eighths  of  the 
human  body  is  water.  Is  always  formed  when 
hydrogen  or  any  substance  containing  hydro- 
gen burns  in  the  air. 


INORGANIC   CHEMISTRY.  \QQ 

The  freezing  point  of  water  is  32°  on  the 
Fahrenheit  scale  of  thermometers,  but  zero  on 
the  Centigrade;  the  boinng  point  is  212°  on  the 
Fahrenheit,  but  1 00  »  on  the  Centigrade.  JVater 
is  expanded  by  heat  and  contracts  on  cooHng, 
but  after  reaching  39°  F.  begins  to  expand 
again  so  that  the  volume  of  a  given  weight  of 
water  is  less  than  the  volume  of  ice  formed 
from  it.  Ice  contracts,  then,  on  melting.  On 
the  other  hand  when  water  is  converted  into 
steam  there  is  great  expansion,  one  volume  of 
water  yielding  1700  volumes  of  steam.  The 
capacity  of  ivater  for  heat  is  greater  than  that 
of  all  bodies  except  hydrogen.  Adoptmg  for 
the  unit  of  measure  that  quantity  of  heat  which 
will  raise  the  temperature  of  one  gram  of 
water  through  one  Centigrade  degree  those 
fractions  of  the  unit  of  heat  which  will  raise 
various  substances,  other  than  hydrogen,  as 
iron,  lead,  or  glass  one  degree  are  called  the 
specific  heats  of  the  substances.  (See  Table 
i).  The  specific  heat  of  hydrogen  is  3.4,  that 
of  iron  0.1138,  that  of  lead  0.0314.  (See  Sec- 
tion 59.) 

Water  has  a  very  general  so  Iveitt  power  vjhich , 
however,  is  limited  and  varies  with  temperature, 
some  substances  being  much  more  soluble  in 
hot  water  than  in  cold  water.  Among  sub- 
stances very  soluble  in  water  we  find  potassium 
carbonate  and  zinc  chloride.    (See  Section  68). 


110  DENTAL   CHEMISTRY. 

Well  waters  on  being*  evaporated  yield  a 
residue  composed  usually  of  compounds  of 
calcium,  mag-nesium,  etc.,  which  have  previ- 
ously been  held  in  solution. 

JVater  enters  into  the  formation  of  crystals, 
readily  shown  by  preparing-  a  saturated  solu- 
tion of  such  salts  as  alum,  potassium  ferro- 
cyanide,  potassium  nitrate,  magnesium  sul- 
phate, and  letting-  stand  in  a  shallow  dish  until 
evaporation  has  taken  place. 

Water  is  the  medium  of  chemical  change. 
(See  Section  141.) 

Water  combines  with  certain  substances, 
forming-  hydrates  with  oxides  of  positive 
elements,  and  anhydrides  with  oxides  of  neg:a- 
tive  elements.  Examples:  quicklime  and  water 
form  slaked  lime;  that  is,  calcium  oxide  and 
water  form  calcium  hydrate;  sulphurous  oxide 
and  water  form  sulphurous  anhydride. 

In  general  water  is  a  limpid,  colorless  liquid, 
odorless,  tasteless,  neutral,  poor  conductor  of 
heat  and  electricity,  773  times  heavier  than  air, 
standard  of  specific  g-ravity.  The  purest 
natural  water  is  rain  water.  This,  however,  is 
somewhat  contaminated  with  matters  washed 
from  the  air.  River  and  lake  waters,  espec- 
ially those  found  in  g-ranitic  regfions,  are  the 
purest  potable  waters.  Mineral  waters  are 
called  alkaline,  sulphurous,  chalybeate,  etc., 
according  to  prevailing-  constituents,  and  con- 


INORGANIC   CHEMISTRY.  ]^21 

tain  usually  larg-e  amounts  of  solids  in  solu- 
tion. 

Use  in  dentistry:  distilled  water  is  used  in 
the  preparation  of  many  dental  formulae.  It  is 
prepared  by  taking;  80  pints  of  water,  distill- 
ing- two  pints  which  are  rejected,  then  distilling 
64  pints.  The  term  aqua,  U.  S.  P.,  is  used  as 
a  name  for  a  solution  of  someg^aseous  or  vola- 
tile body  in  water.  Thus,  aqua  chlori;  the  term 
liquor  is  used  when  the  substance  dissolved  is 
fixed  or  solid,  as  Liquor  PlumM  Subacetatis. 

178.    Hydrogen  Dioxide.— 

Synonyms:  hydrogen  peroxide,  hydric  diox- 
ide or  peroxide,  oxygenated  water. 

Theoretical  constitution:  H2O2,  hydrogen 
dioxide,  composed  of  two  atoms  of  hydrogen 
and  two  of  oxygen;  by  weight,  32  of  oxygen  to 
2  of  hydrogen,  or  16  to  i .    Molecular  weight,  34. 

Preparation :  pass  a  stream  of  carbon 
dioxide  through  water  containing  barium 
dioxide  in  suspension: 

BaO^  +  CO2  +  H2O    =    BaCOa  +  H^O^. 

Barium  dioxide    carbonic  dioxide    water  barium  carbonate         hydric  dioxide. 

Properties:  in  the  purest  form  it  is  a  syrupy 
colorless  liquid,  having  an  odor  like  chlorine 
or  ozone,  and  a  tingling,  metallic  taste.  It  is 
never  used  in  the  purest  undiluted  form  in  den- 
tal operations  owing  to  the  readiness  with  which 
it  decomposes  and  gives  off  its  oxygen.  It  is 
a  powerful  antiseptic,  colorless,  odorless,  cleans- 


112  DENTAL   CHEMISTRY. 

ingf  and  stimulating,  does  not  stain  or  corrode, 
and  is  not  poisonous.  It  gives  off  its  oxygen 
with  effervescence  in  contact  with  many  sub- 
stances and  notably  with  pus.  Application  to 
dentistry:  it  effervesces  with  pus,  giving  off  nas- 
cent oxygen,  which  is  a  powerful  bactericide; 
being  one  of  the  most  cleansing  of  agents,  it  is 
used  to  clean  cavities.  Combined  with  weak 
alkali  it  bleaches.  A  "ten  volume"  solution  of 
it  is  one  which  will  give  off  ten  parts  by  vol- 
ume of  oxygen;  that  is,  one  measure  of  it  gives 
off  ten  measures  of  oxygen.  A  "two  volume" 
solution  contains  0.4  per  cent,  of  the  pure 
dioxide.  A  little  acid  is  added  to  the  solutions 
of  the  dioxide  commonly  used  in  dentistry  as 
an  aid  to  their  stability.f  Hydrogen  dioxide 
should  be  kept  in  a  cool  place  in  a  glass-stop- 
pered bottle.  Hydrogen  dioxide  is  sometimes 
used  in  solution  in  glycerine  instead  of  in 
water.  It  gives  off  its  oxygen  more  slowly 
than  when  in  aqueous  solution. 

179.  Iodine. — Symbol:  I.  Atoms  in  molecule:  X^.  Atomic 
weight:  127.  Molecular  weight:  254.  Density:  127.  Spe- 
cific gravity :  4.95.  Weight  of  07ie  litre  of  gas:  11.37  gram- 
mes. How  liquefied:  at  225°  F.  Solubility  in  water:  7000 
parts  of  water  dissolve  i  of  iodine.  Freely  soluble  in 
alcohol  and  in  aqueous  solution  of  potassium  iodide. 
Occurrence  in  nature:  in  combination,  as  iodides,  etc,  How 
made:    from  ashes  of  sea-weed.      By  action  of   chlorine 

fRollins  has  found  that  as  ordinarily  obtained  it  acts  perceptibly 
on  the  teeth,  and  hence  should  be  used  with  caution. 


INORGANIC   CHEMISTRY  113 

and  heat  on  liquor  obtained  by  leaching  sea-weed  ashes. 
Properties:  solid,  in  brilliant  scales,  of  gray  metallic  color. 
Gives  off  violet  vapors.  Imparts  yellowish-brown  stain 
to  skin.  Solutions  when  cold  give  blue  color  to  boiled 
starch.  Not  so  corrosive  or  poisonous  as  bromine,  but 
yet  poisonous  in  sufficient  quantity.     Antidote,  starch. 

Preparations  used  in  dental  pharmacy.— 

Tincture  of  iodine,  Tinctura  lodi,  is  made  of 
80  grams  of  iodine  in  920  g'rams  of  alcohol. 
Compound  solution  of  iodine,  Liquor  lodi 
Compositus  is  iodine  50  grams,  potassium 
iodide  100  grams,  distilled  water  850  C.  c.  De- 
colorized tincture  of  iodine,  Tinctura  lodi  De- 
colorata,  is  iodine  40  grams,  alcohol  400 
C.  c,  stronger  water  of  ammonia  90  C.  c.  Car- 
bolized  iodine  solution.  Liquor  lodi  Phenola- 
tus,  is  tincture  of  iodine  i  gram,  phenol  (car- 
bolic acid)  12  centigrams,  glycerine  8  grams, 
water  45  C.  c;  it  is  a  colorless  liquid. 
The  antidote  for  iodine  is  starch. 

Bromine. — Symbol:  Br.  Atoms  in  molecule:  Brg. 
Atomic  weight:  8o.  Molecular  weight :\6o.  De7isity :  8o. 
Specific  gravity:  3.187.  Weight  of  one  litre  of  gas:  7.15 
grammes.  How  liquefied:  at  ordinary  temperatures.  Sol- 
nbility  in  zvater:  33   parts  water  dissolve  one  of  bromine. 

Occurrence  in  nature:  in  combinations  as  bromides,  etc. 
How  made:  action  of  sulphuric  acid  on  bittern  in  presence 
of  manganese  dioxide.  Properties:  liquid,  heavy,  dark, 
brownish-red,  less  active  than  chlorine,  bleaches,  burns, 
is  poisonous,  colors  starch  yellow.  Fumes  violently.  Is 
heavier  than  some  metals,  as  aluminium. 

180.     Chlorine. — Symbol:  CI.   Atoms   in    molecule:    Clg. 


114  DENTAL   CHEMISTRY. 

Atomic  weight :  35.4.  Molecular  tueight:  71.  Density:  35.4. 
Specific  gravity :  2.47.  Weight  of  one  litre  of  gas:  3.17  gram- 
mes. How  liquefied:  4  atmospheres  or — 40°  F.  Solubility 
in  water:  i  part,  by  volume,  of  water  dissolves  nearly 
three  volumes  of  chlorine  gas.  Occurrence  in  nature: 
always  in  combination,  usual  source  common  salt.  How 
made:  {a)  action  of  H2SO4  on  NaCl  in  presence  of  Mn 
O2;  (b)  action  of  air  on  moistened  "chloride  of  lime," 
Properties:  is  a  gas,  greenish-yellow,  of  pungent  taste  and 
suffocating  odor,  wholly  irrespirable,  powerful  bleaching 
agent  and  disinfectant.  Combines  with  all  elements  ex- 
cept oxygen,  nitrogen,  and  carbon. 

Use  in  dentistry. — Chlorine  g-as  has  been 
used  to  bleach  discolored  teeth.  It  may  be 
prepared  as  follows: 

Place  20  parts,  by  weight,  of  commercial  hy- 
drochloric acid  (sp.  gr.  about  1.16)  in  a  flask, 
add  8  parts  manganese  dioxide,  agitate,  and 
after  a  time  heat  the  flask  on  a  sand  bath 
(safety-tube  may  be  used,  which  is  a  funnel- 
tube  bent  twice  on  itself).  The  equation  is  as 
follows: 

4HCI  +  MnO^  =  MnCl^  +  2H2O  +  Cl^. 

The  flask  should  be  closed  by  a  cork  perfor- 
ated by  two  holes,  through  one  of  which  the 
safety-tube  may  be  inserted,  its  lower  end  dip- 
ping below  the  surface  of  the  acid;  through 
the  other  hole  a  short  glass  tube  bent  at  right 
angles  should  be  inserted,  its  lower  aperture 
.being  about  an  inch  below  the  cork.  The  gas 
escapes  through  this  second  tube,  called  deliv- 


INORGANIC    CHEMISTRY.  115 

ery  tube,  and  may   be  collected  in  any  way 
desired. 

Chlorine  water  is  used  in  dental  practice  as  a 
local  application.  It  is  prepared  by  passing- 
the  g"as  into  water  in  which  it  is  readily  solu- 
ble, one  volume  of  water  dissolving  three  vol- 
umes of  chlorine  gas.  The  solution  Aqua 
Chlori,  U.  S.  P.,  is  a  greenish-yellow  liquid, 
slowly  changing  in  the  light  to  hydrochloric 
acid.  It  should  not  redden  litmus  but  bleach 
it.  It  should  be  kept  in  a  glass-stoppered 
bottle  away  from  the  light  and  in  a  cool  place. 
It  should  contain  0.4  per  cent  of  chlorine. 

Toxicology. — Chlorine  gas  is  an  irritant  poison,  and  is 
irrespirable,  causing  inflammation  of  the  air  passages. 
The  treatment  is  instant  removal  to  fresh  air,  inhalation 
of  ammonia  or  very  dilute  sulphuretted  hydrogen  or  ether- 
vapor.     The  inhalation  of  steam  is  said  to  be  beneficial. 

181 .    Compounds  of  chlorine. — 
Hydrogen  Chloride  or  Hydrochloric  Acid. 

Synonyms:  muriatic  acid,  chlorhydric  acid, 
Acidum  Hydrochloricum. 

Theoretical  constitution:  HCl,  a  hydracid, 
binary  compound  composed  of  one  atom  of 
hydrogen  and  one  of  chlorine;  by  weight  35.4 
parts  chlorine  to  i  of  hydrogen.  Molecualr 
weight  36.4.  Density  of  the  gas,  18.25;  sp.  gr. 
1.264.  Absolute  HCl  contains  97.26  per  cent, 
of  chlorine  and  2.74  per  cent,  of  hydrogen. 

Preparation:  found  free  in  small  quantities 


116  DENTAL   CHEMISTRY. 

in  g^astric  juice.     Made    from    common  salt 
and  sulphuric  acid: 

H2SO4  +  2NaCl  =  2HCI  +  Na^SO* 

Sulphuric  acid       sodium  chloride    hydrochloric  acid    sodium  sulphate. 

Properties:  colorless,  transparent  gas  of 
pungent  odor,  strongly  acid  reaction,  very  sol- 
uble in  water,  one  volume  of  which  dissolves 
450  volumes  of  the  gas  forming  the  ordinary 
muriatic  acid.  Commercial  muriatic  acid  is 
yellow,  and  the  strongest  contains  25  to  30  per 
cent,  of  the  gas.  Acidiiin  Muriaticum  or  Aci- 
dum  Hydrochloricum,  U.S.  P.,  is  colorless,  sp. 
gr.  1. 16,  contains  31.9  per  cent  of  the  gas. 
Acidurn  Muriaticttm  Dihttimi,  U.  S.  P.:  strong 
acid  6  parts,  distilled  water  13  parts;  sp.  gr., 
1.049. 

Use  in  dentistry:  it  is  used  as  a  solvent  for 
zinc,  and  sometimes  as  a  local  application.  It 
dissolves  iron  and  zinc  readily  and,  when  warm- 
ed, attacks  tin. 

Toxicology. — Hydrochloric  acid  is  a  corrosive  poison, 
caustic  and  escharotic.  It  stains  the  skin  at  first  white, 
then  produces  discoloration.  The  stain  on  black  cloth 
is  red,  gradually  disappearing  in  course  of  time.  Burns 
by  the  acid  should  be  treated  first  by  washing  the  acid  off 
well,  then  by  application  of  sodium  bicarbonate  solution 
and  oil.  If  the  acid  be  taken  internally,  give  at  once 
magnesia  or  bicarbonate  of  sodium  in  milk  at  short  inter- 
vals, then  bland  liquids  as  raw  eggs,  gruel,  or  oil. 

182.  Fluorine. — Symbol:  F'orFl.  Atoms  hi  molecule:  Flo. 
Atomic  weight:  19.  Revised  zucight:  18.9840.  Molecular 
weight:    38.     Density:   19.     Weight  of  one  litre  of  gas:   1.7 


INORGANIC   CHEMISTRY. 


117 


Dyads  positive 
to  hydrogen. 


grammes.  Occurrence  in  nature:  in  combination  as  in 
fluor-spar  and  cryolite  which  are  fluorides.  How  made: 
cannot  be  readily  isolated.     Properties:  colorless  gas. 

183.  Dyads. — The  dyads  of  importance  will  be  studied 
in  the  same  relative  order  as  the  monads. 

Table  16.    Dyads  of  Importance. 

Barium 
Calcium 
Mag-nesium 
.  Zinc 
Cadmium 
Lead 
Uranium 
Copper 
Mercury 

Tellurium 

Sulphur 

Oxyg-en 

184.  Barium. — Symbol:  Ba;  Latin  7iame:  Barium. 
Equivalence :  W.  Specific  gravity:  4.  Atomic  wt.  {approx.)  : 
136.8.  Atomic  wt.  {^revised):  136.763.  Electrical  state :  +. 
Fusing  point:  below  red  heat.  Properties:  malleable, 
decomposes  water,  gradually  oxidizes. 

Compounds  of  barium. — Barium  chloride,  BaClg,  and 
barium  nitrate,  Ba(N03)2,  are  both  soluble  in  water  and 
are  used  in  laboratory  work  in  testing  for  sulphuric  acid 
and  sulphates. 

185.  Calcium. — Symbol:  Ca;  Latiti  name:  Calcium. 
Equivalence :  II.  Specific  gravity:  1.58.  Atomic  weight 
{approx.) :  i![0.  Atomic  weight  {revised'):  39.99.  Electrical 
state :  +.  Fusing  point:  burns  when  heated.  Properties: 
light  yellow  metal,  about  as  hard  as  gold,  very  ductile, 
tarnishes  slowly,  decomposes  water. 


Dyads  neg"ative  to 
hydrogen. 


118  DENTAL   CHEMISTRY. 

1 86.  Calcium  compounds.  Calcium  Sul- 
phate.— 

Synonyms:  sulphate  of  v,alcium,  sulphate  of 
lime,  plaster-of-Paris,  calcic  sulphate.  Official 
name,  Calcii  Sulphas. 

Theoretical  constitution:  CaS04.2H20,  one 
atom  of  calcium,  one  of  sulphur  and  four  of 
oxygen;  by  weight  40  parts  calcium,  32  parts 
sulphur,  64  parts  oxygen.  Molecular  weight, 
172. 

Preparation:  calcium  sulphate  occurs  in  na- 
ture as  a  mineral  called  gypsum.  Gypsum, 
however,  differs  from  the  dried  calcium  sul- 
phate of  commerce  in  that  it  contains  two  mol- 
ecules of  water  of  crystallization;  the  full 
formula  for  gypsum  is,  therefore,  CaSO*, 
2H2O.  Ground  gypsum  is  called  terra  alba. 
Gypsum  when  heated  to  392^^  F.  loses  its  water 
of  crystallization,  becoming  changed  into  a 
white,  opaque  mass  having  CaSO*.  without  any 
H2O,  for  its  formula.  This  substance  when 
ground  is  known  as  plaster-of-Paris  and  is  an- 
hydrous calcium  sulphate;  it  readily  recom- 
bines  with  water,  becoming  a  hard  mass  on 
the  addition  of  H2O. 

Properties  and  uses:  the  anhydrous  sulphate, 
CaSOi,  plaster-of-Paris,  is  a  hard,  white,  nearly 
insoluble  substance.  After  taking  up  water  it 
"sets"  into  a  stone-like  solid,  and  hence  is  use- 
ful in  making  moulds,  casts,  and  immovable 


INORGANIC   CHEMISTRY. 


119 


surg-ical  dressing's.  If  alum  and  gelatine  be 
mixed  with  the  plaster-of-Paris  before  addition 
of  water,  it  forms  a  harder  and  less  porous  mass 
than  the  plaster  alone,  and  presents  a  smooth 
surface  which  can  be  washed  with  water  con- 
taining" the  various  disinfecting-  agents. 

187.    Calcium  Carbonate. — 

Synonyms:  calcic  carbonate,  Calcis  Car- 
bonas,  carbonate  of  lime.  Official  name,  Cal- 
cii  Carbonas  Praecipitatus. 

Theoretical  constitution:  CaCOa,  one  atom 
of  calcium,  one  of  carbon,  three  of  oxyg^en;  by 
weight  40  parts  calcium,  12  carbon,  48  oxygen. 
Molecular  w^eight,  100. 

Origin  and  method  of  preparation:  it  occurs 
more  or  less  pure  in  nature  as  chalk,  limestone, 
marble,  Iceland  spar,  coral,  shell,  etc.  It  is 
found  in  the  bones,  teeth,  saliva,  and  in  cal- 
culi and  tartar. 

It  is  obtained  for  dental  uses  ( i )  by  precipi- 
tation, by  mixing  solutions  of  calcium  chloride 
and  sodium  carbonate: 

Na^COa  +  CaCl^  =  CaCOs  +  2NaCl 

Sodium  _i_      Calcium       ___        Calcium        _L        Sodium 

carbonate  '        chloride  carbonate         '^        chloride 

(2)  as  prepared  chalk  (Creta  Praeparata)  by 
grinding  a  native  chalk  in  water,  allowing  the 
mixture  to  settle,  decanting  the  upper  portion, 
collecting  and  drying  the  finer  particles. 

Properties  and  uses:  precipitated  calcium 
carbonate  is  a  neutral,  white,  tasteless,  impal- 


120  DENTAL   CHEMISTRY. 

pable  powder;  it  is  insoluble  in  pure  water  and 
in  alcohol,  but  soluble  in  water  containing  car- 
bonic dioxide  (carbonic  acid).  It  is  found  as 
acid  carbonate,  dissolved  in  almost  all  natural 
waters,  causing-  hard^tess,  which  may  be  re- 
moved by  boiling,  hence  called  "temporary" 
hardness. 

It  is  used  in  dentistry  as  a  polishing  powder, 
as  an  ingredient  of  dentifrices,  and  as  an  ant- 
acid. It  is  useful  as  an  antidote  in  cases  of 
poisoning  by  acids. 

1 88.  Calcium  Oxide. — 

Synonyms:  calcic"  oxide,  lime,  Calx,  quicklime,  burned 
lime.     Official  name,  Calcii  Oxidum. 

Theoretical  constitution;  CaO,  calcium  oxide,  one  atom 
of  calcium  and  one  of  oxygen  in  its  molecule;  by  weight, 
40  parts  of  calcium  to  16  of  oxygen.  Molecular 
weight,^56. 

Preparation;  lime  is  obtained  on  a  large  scale  by  heat- 
ing limestone  or  other  calcium  carbonate  in  a  lime  kiln: 
CaCO^        =  CaO        +         CO, 

Calcium  Calcium  .  Carbon 

carbonate  =  oxide  "t"  dioxide. 

For  pharmaceutical  purposes  it  is  made  by  heating  mar- 
ble in  a  Hessian  crucible. 

Properties  and  uses:  lime  is  a  grayish-white  amorph- 
ous solid,  odorless,  infusible,  of  alkaline  taste  and  reaction. 
It  becomes  incandescent  in  the  oxy-hydrogen  flame, 
emitting  a  very  intense  white  light.  Made  from  marble 
it  should  be  pure  white. 

189.  Calcium  Hydrate. — Slaked  lime,  Calcii  Hydras. 
Formula,  Ca(  HO  )2.  Molecular  weight,  74.  Prepared  by 
adding  10  parts  water  to  16  of  lime,  letting  cool,  and 
straining.     Dry,  white,  odorless,  tasteless,  alkaline  pow- 


INORGANIC   CHEMISTRY  121 

der.  None  but  recently  prepared  calcium  hydrate  should 
be  used,  as  it  soon  becomes  carbonate,  absorbing  carbonic 
dioxide  from  the  air. 

Mortar  is  a  mixture  of  sand,  water,  and  slaked  lime;  as 
the  water  evaporates  mortar  hardens,  because  part  of  the 
lime  becomes  a  carbonate,  absorbing  carbon  dioxide  from 
the  air,  and  part  a  silicate  combining  with  the  silicic  acid 
of  the  sand. 

Cement  or  hydraulic  mortar  is  a  mixture  of  powdered 
quartz,  lime,  and  aluminium  silicate;  its  hardening  is  due 
to  the  formation  of  calcium  and  aluminium  silicates. 

Lime  Water  or  Liquor  Calcis  is  a  clear  solu- 
tion of  calcium  hydrate  in  water.  Sugar  in- 
creases the  solubility  of  the  calcium  hydrate. 
Lime  water  is  a  colorless,  nearly  odorless 
liquid,  of  feebly  caustic  taste  and  alkaline  re- 
action. It  is  a  solution  of  about  15  parts  cal- 
cium hydrate  in  10,000  of  water. 

Milk  of  lime  is  lime  water  containing  an  ex- 
cess of  calcium  hydrate,  rendering  it  turbid. 

Lime  water  is  used  in  dentistry  in  form  of 
gargle  as  an  antacid,  astringent,  etc. 

190.    Calcium  Fluoride. — 

Synonyms:  fluor-spar,  fluoride  of  lime,  Calcii  Fluor- 
idum. 

Theoretical  constitution:  CaFlg,  one  atom  of  calcium 
and  two  of  fluorine,  40  parts  by  weight  of  calcium,  and  38 
of  fluorine.     Molecular  weight,  78. 

Preparation:  calcium  fluoride  occurs  in  nature  as  fluor- 
spar; it  is  made  artificially  by  treating  a  salt  of  calcium 
with  potassium  fluoride. 

Properties:  human  bone  contains  about  two  per  cent, 
of  calcium  fluoride;  the  enamel  of  teeth  contains  it  also. 


122  DENTAL    CHEMISTRY. 

It  is  a  very  hard  substance,  insoluble  in  water,  but  de- 
composed by  sulphuric  acid,  hydrofluoric  acid  being 
formed. 

191.  Calcium  Sulphite.— Sulphite  of  lime,  Calcii  Sul- 
phis.  Formula  CaSOs,  2H2O.  Molecular  weight,  156. 
Made  by  saturating  milk  of  lime  with  sulphurous  oxide, 
collecting,  and  drying  the  precipitate.  It  is  a  white  pow- 
der, slightly  soluble  in  water,  soluble  in  sulphurous 
acid.  It  gradually  becomes  converted  to  sulphate.  Used 
as  an  antiseptic. 

192.  Chlorinated  Lime.— Official  name, 
Calx  Chlorata.  Contains  probably  Ca(C10)2, 
calcium  hypochlorite.  It  should  yield  25  per 
cent,  chlorine  on  addition  of  acid.  It  is  pre- 
pared by  the  action  of  chlorine  on  calcium 
hydrate.  It  is  a  white  or  g'rayish-white,  dry  or 
but  slightly  damp  powder  or  friable  lumps,  of 
feeble  chlorine-like  odor,  and  disag-reeable, 
saline  taste.  It  should  be  kept  in  well-closed 
vessels,  in  a  cool,  dry  place.  It  is  partially 
soluble  in  water  and  in  alcohol.  It  is  a  disin- 
fectant and  a  bleaching-  agent.  It  is  used  in 
dentistry  as  a  deodorizer,  disinfectant,  anti- 
septic, and  bleaching  agent.  It  is  poisonous 
in  large  doses. 

193.  Calcium  Phosphate.— CaaC  P04)2,  basic 
phosphate,  tricalcic  phosphate,  bone  '  phos- 
phate: found  in  whole  organism,  constitutes 
two-thirds  of  the  teeth,  found  in  bones  and  in 
calculi;  in  the  ash  of  albuminous  substances; 
white,  insoluble.  Readily  soluble  in  acid  solu- 
tions. 


INORGANIC   CHEMISTRY. 


123 


194.  Calcium  Hypophospliite.— Ca(H2P02)2  =  170. 
Prepared  by  dissolving  phosphorus  in  milk  of  lime  by 
aid  of  heat.  Is  a  white  salt,  permanent  in  air,  soluble  in 
water,  insoluble  in  alcohol. 

195.  Magnesium. — Symbol:  Mg.;  Latin  name:  Mag- 
nesium. Equivalence:  11.  Specific  gravity:  1. 70  to  1.74. 
Atomic  tvt.  {approx.):  24.  Atomic  wt.  {revised):  23.959. 
Electrical  state :  +.  Fusing  point:  melts  at  red  heat.  Pw/^r- 
ties:  magnesium  is  a  brilliant,  silver-white  metal,  lighter 
than  silver  or  aluminium,  tarnishing  in  damp  air,  burn- 
ing easily  and  with  a  flame  of  dazzling  brightness.  It  is 
soluble  in  dilute  acids  and  unites  directly  with  most  of  the 
negative  elements. 

■  Table  17. — Compounds  of  Magnesium. 


Name. 

Chloride 
Oxide 

Sulphate 

Phosphate 

Ammonio-mag- 
nesium  phos- 
phate 

Hypochlorite 


Formula. 

MgCU 
MgO 


MgSOi 


Mg3(PO,)2 

MgNHiPO, 
Mg(C10)2 


Propertien,  Uses,  etc. 

White,  soluble,  very  bitten 

Known  as  magnesia  or  cal- 
cined magnesia.  White,  in- 
fusible, antacid,  antidote  to 
arsenic  and  caustic  acids. 

"Epsom  salts."  White,  sol- 
uble, very  bitter. 

Found  in  body  along  with 
calcium  phosphate. 

Called  triple  phosphate. 
Very  soluble  in  acids,  in- 
soluble in  alkalies. 

Used  forbleachingpurposes. 


196.    Magnesium  Carbonate.— 

Synonyms:  carbonate  of  magnesia,  mag"- 
nesia  alba,  salis  amari.  Official  name,  Mag- 
nesii  Carbonas. 

Formula,  4MgC03.Mg(HO)2.H20. 


124  DENTAL   CHEMISTRY. 

Two  kinds  are  known  to  pharmacy,  the 
"  heavy  "  and  the  "  Hght."  Both  are  prepared 
by  dissolving-  25  parts  of  magnesium  sulphate 
and  20  of  sodium  carbonate,  each  separately, 
in  water,  but  the  "  lig'ht "  carbonate  is  the 
result  of  mixing-  the  solutions  when  cold,  the 
"  heavy  "  by  dissolving  in  hot  water  and  mix- 
ing while  hot.  There  are  certain  other  differ- 
ences also  in  the  methods  of  preparation,  the 
light  carbonate  solution  being  much  more 
dilute  than  the  heavy.  The  light  carbonate 
contains  more  carbonate  and  less  hydrate,  is 
about  three  times  as  bulky,  and  is  partly 
crystalline.  The  heavy  carbonate  is  wholly 
amorphous.  Both  form  a  light,  white  mass  or 
powder,  nearly  insoluble  in  water,  but  readily 
soluble  in  dilute  acids. 

197.    Zinc— 

Symbol'.  Zn.;  Latin  name:  Zincum.  Equivalence.  II. 
Specific  gravity.  7.10107.20.  Atomic  weight'.  65.  Revised 
atomic  weight:  64.904.  Electrical  state:  +•  Fusing  point: 
773°  F.  Length  of  bar,  etc.:  1.0029;  (2d  in  rank,  cadmium 
=  i).  Wt.  of  cubic  ft.  in  lbs.:  445.7.  Tensile  strength'. 
3.3  to  8.3.  Te?iacit)>:  2;  (8th  rank).  Malleability:  7; 
(7th  rank).  Brittle,  until  heated  to  between  248°  and 
302°  F.  Ductility:  8;  (8th  rank).  Conducting  power  i^he  at): 
5;  (5th  rank).  Conducting  power  {^electricity):  290  (silver 
=  icoo);  (4th  rank).  Resistance  to  air,  etc.:  tarnishes 
slowly;  in  moist  air  becomes  coated  with  carbonate.  Sol- 
ubility: soluble  in  dilute  acids,  and  in  solutions  of  alkaline 
hydrates;  slowly  corroded  by  water,  milk,  and  wine. 

Direct    combinations:     oxygen,    chlorine.       With    iron, 


INORGANIC   CHEMISTRY.  225 

when  heated  to  fusion.  Color  and  appearance',  bluish- 
white.  Structure',  crystalline;  form  of  crystals,  rhombo- 
hedral.  Consistence',  brittle.  Compowids'.  zinc  as  zinc 
sulphide,  zinc  chloride,  etc.  Alloys',  brass,  bronze,  bell 
metal,  German  silver,  Aich's  metal,  arguzoid,  Dutch 
metal,  electrum,  Muntz's  metal,  solders,  sterro-metal, 
tutenag. 

Occurrence:  zinc  is  found  usually  either  as 
sulphide,  zinc-blende,  ZnS.  or  as  carbonate, 
calamine,  ZnCOj.  It  is  also  found  as  silicate 
and  as  oxide.  Blende  is  found  in  Great  Britain, 
Saxony,  Aix-la-Chapelle,  and  in  North 
America.  Calamine  occurs  in  Great  Britain, 
Aix-la-Chapelle,  Silesia,  Spain,  and  in  many 
other  places.  Red  zinc  ore  or  oxide  is  found 
chiefly  in  New  Jersey. 

Preparation:  zinc  is  converted  into  vapor 
with  comparative  facility;  it  boils  and  distills  at 
bright  red  heat.  Hence,  in  order  to  extract 
zinc  from  its  ores,  the  latter  are  first  calcined, 
that  is  ignited  in  the  air  so  as  to  burn  off  any 
oxidizable  material,  and  the  zinc  obtained  in 
form  of  oxide.  The  latter  is  then  mixed  with 
carbon  and  distilled,  carbonic  acid  gas  and 
zinc  vapor  being  formed;  the  zinc  vapor  is 
condensed  in  suitable  receivers. 

Properties:  under  ordinary  circumstances 
zinc  is  brittle,  but  when  heated  to  about  300° 
F.,  it  becomes  malleable  and  ductile,  and  may 
be  rolled  into  thin  sheets.  At  about  400*"  F., 
it  becomes  brittle,  melts  at  775°  and  at  1842° 


126  DENTAL   CHEMISTRY. 

boils,  volatilizes,  and  burns,  if  air  be  not  ex- 
cluded, with  a  fine  greenish-white  light,  the 
oxide  being  formed. 

Galvanized  iron  is  iron  covered  with  a  coat- 
ing of  metallic  zinc. 

Dental  uses:  accordingto  Flagg,  zinc,  in  pro- 
portion of  from  I  to  i>^  parts  in  loo,  if  added 
to  the  usual  40  silver  60  tin  alloys,  seems  to 
control  shrinkage,  imparts  a  "buttery"  plas- 
ticity to  the  amalgam,  adds  to  the  whiteness  of 
the  filling,  and  assists  in  maintaining  its  color. 

Zinc  is  used  in  making  dies  for  swaging 
plates.  It  may  be  used,  according  to  Essig,  in 
making  counter-dies."* 

198.    Alloys  of  Zinc. — 

Zinc  and  tin  alloy  for  casting  dies  for  swaging 
plates  is,  according  to  Richardson,  zinc  4,  tin  i. 

Zinc  in  Solders. — Solders  made  of  the  common  com- 
mercial zinc  are  brittle,  and  are  rolled  with  difficulty. 
They  cause  also  a  strong,  brassy  taste  in  the  mouth,  and 
should  therefore  be  dissolved  out  of  the  finished  work  by 
pickling  in  nitric  acid,  the  surface  afterwards  being  burn- 
ished.    Pure  zinc  in  solders  gives  a  plate  that  rolls  easily, 


♦Dies  for  making  artificial  teeth.    [Rollins  in  Boston  Medical  and 
Surgical  yournal,  1884]. 

Metal  plates  are  not  as  firm  as  rubber  because  they  do  not  repre- 
sent so  perfect  a  reverse  of  the  mouth.  This  is  mostly  due  to  the 
imperfect  character  and  softness  of  the  metal  dies  on  which  they  are 
struck.  A  perfect  die  can  be  made  by  preparing  the  surface  of  the 
impression  for  electrotyping  and  then  depositing  copper  on  it  which 
if  the  die  is  to  be  used  for  striking,  can  be  backed  with  a  harder 
metal  to  the  right  firmness  and  form.  Such  a  die  is  perfect  and 
harder  than  any  now  in  use. 


INORGANIC   CHEMISTRY.  127 

makes  a  handsome  solder  and  causes  much  less  of  the 
brassy  taste,  so  little  indeed  that  most  people  do  not  per- 
ceive it.     (Chandler.) 

199.    Compounds  of  Zinc:  Zinc  Cliloride. 

Synonyms:  butter  of  zinc,  muriate  of  zinc. 
Official  name,  Zinci  Chloridum. 

Theoretical  constitution:  ZnC\,  one  atom  of 
zinc  and  two  of  chlorine  in  the  molecule;  by 
weight,  64.9  parts  of  zinc  to  70.8  of  chlorine. 
Molecular  weight,  135.7.  It  contains  47.83  per 
cent  of  zinc. 

Preparation,  properties,  and  uses:  zinc  chlo- 
ride is  made  by  heating-  zinc  in  a  current  of 
chlorine,  or  by  the  action  of  hydrochloric  acid 
on  granulated  zinc  or  zinc  carbonate,  and 
evaporation  of  the  solution  to  dryness. 

It  occurs  in  the  form  of  hard,  dirty-white 
masses,  very  deliquescent,  and  forming  a  clear 
solution  with  water.*  Zinc  chloride  has  a 
caustic,  sharp  taste,  and  is  acid  in  reaction.  It 
is  soluble  in  alcohol  and  in  ether.  "  Burnett's 
Disinfecting  Fluid  "  contains  zinc  chloride,  in 
proportion  of  from  205  to  230  grains  to  the 
ounce  of  water.  The  official  solution  of  chlo- 
ride of  zinc.  Liquor  Zinci  Chloridi,  is  an  aque- 
ous solution  of  zinc  chloride  containing  50  per 
cent,  of  the  latter,  or  23.92  per  cent,  of  zinc. 

It  is  made  from  20  parts  of  granulated  zinc,  i  part  of 
nitric  acid,  i  part  of  precipitated  carbonate  of  zinc,  and 

*It  is  one  of  the  most  soluble  substances  known. 


128  DENTAL   CHEMISTRY. 

sufficient  hydrochloric  acid  and  distilled  water.  To  the 
zinc,  enough  hydrochloric  acid  is  added  to  dissolve  it; 
the  solution  is  filtered,  nitric  acid  added,  the  whole 
evaporated  to  dryness,  and  the  dry  mass  brought  to 
fusion.  After  cooling,  it  is  dissolved  in  15  parts  distilled 
water,  the  precipitated  carbonate  of  zinc  added,  and  the 
mixture  agitated  occasionally  during  the  24  hours.  Fin- 
ally it  is  filtered  through  washed  asbestos  free  from  iron, 
and  enough  distilled  water  added  to  it,  through  the  filter, 
to  make  the  product  weigh  80  parts.  The  reaction  is  as 
follows: 

Zn      +      2HCI      =      ZnCU      +      H2. 

Zinc  hydrochloric  zinc  hydrogen 

acid  chloride 

The  solution  is  evaporated  to  dryness,  and  the  dry  mass 
fused  in  order  to  remove  any  excess  of  nitric  acid.  Zinc 
chloride  solution  cannot  be  filtered  through  paper;  pow- 
dered washed  glass  or  purified  asbestos  must  be  used. 

The  solution  is  a  heavy,  strongly  caustic  liquid,  which 
should  mix  with  alcohol  without  precipitation.  Its  sp. 
gr.  is  i.555.t 

If  of  a  sp.  gr.  of  1. 1275  at  68°  F.,  it  contains  only  13.876 
per  cent  of  zinc  chloride;  if  its  sp.  gr.  is  1.2466  it  con- 
tains 25.819  per  cent;  if  1.3869,  37.483  per  cent. 

Use  in  dentistry:  zinc  chloride  is  used  in  den- 
tal medicine  for  various  purposes  as  an  anti- 
septic, disinfectant,  and  deodorizer.  A  solution 
of  it  is  used  in  connection  with  the  oxide,  to 
make  a  plastic  filling  (see  zinc  oxychloride). 

Toxicology:  chloride  of  zinc  rapidly  coagulates  albu- 
min. It  is  a  caustic  and  irritant.  Externally  applied,  it 
penetrates  deeply  into  tissues  and  spreads,  producing  a 
white,  thick,  and  hard  eschar.    In  cases  of  poisoning  from 

fA  solution  of  this  strength  is  used  in  making  the  oxychloride 
cement. 


INORGANIC   CHEMISTRY.  129 

internal  administration,  carbonate  of  sodium  in  milk, 
white  of  egg,  or  soap  are  the  antidotes. 

200.  Zinc  Oxide.  —  Official  name,  Zinci 
Oxidum.  ZnO  =  80.9.  Made  on  a  large 
scale  by  heating  metallic  zinc  in  a  current  of 
air.  To  make  a  pure  white  zinc  oxide  for 
pharmaceutical  purposes,  pure  precipitated 
zinc  carbonate  should  be  heated  at  low  red  heat 
until  the  water  and  carbonic  oxide  are  wholly- 
expelled.  This  can  be  done  below  500°  F. 
The  reaction  is  as  follows: 

2(ZnC03).3Zn(HO).  =  sZnO  +  2CO2+  3H2O 

Zinc  carbonate  zinc  oxide  carbonic  acid  water 

Too  high  heat  will  give  the  product  a  yellow 
color,  and  make  it  feel  harsh.  A  small  quantity 
should  be  used  in  heating.  A  good  quality  of 
zinc  oxide  should  come  in  the  form  of  a  soft, 
flaky,  impalpable  powder  of  sp.  gr.  5.6.  It 
should  turn  yellow  when  heated  in  a  test  tube, 
and  become  white  again  on  cooling. 

It  is  insoluble  in  water  but  completely  solu- 
ble in  dilute  acids.  It  is  not  darkened  by 
sulphuretted  hydrogen. 

201.  Zinc  Oxyphosphate.— By  the  combi- 
nation of  zinc  oxide  with  phosphoric  acid  a  sub- 
stance is  obtained  known  familiarly  as  oxyphos- 
phate  of  zinc.  As  known  to  dentists  it  comes 
in  the  form  of  a  powder  and  a  liquid.  The  pow- 
der is  zinc  oxide,  and  the  liquid  some  variety  of 
phosphoric  acid.    The  two  mixed,  in  propor- 


130  DENTAL   CHEMISTRY. 

tions,  found  by  trial  to  be  suitable  for  setting" 
purposes,  form  the  oxy phosphate  cement. 

When  glacial  phosphoric  acid  is  used,  the  cement  is 
termed  oxywz^/Vzphosphate.  The  pure  glacial  phosphoric 
acid  is  preferred  for  use,  as  cements  made  from  the  com- 
mercial glacial  acid  have  been  found  less  durable.* 

202.    Zinc  Oxyicliloride. — 

Theoretical  constitution:  oxychlorides  differ 
from  chlorides,  in  that  the  former  are  chlorides 
of  the  oxide  of  a  metal,  while  the  latter  are 
chlorides  of  the  metal  itself  only. 

There  are  various  oxychlorides  of  zinc,  whose  formulae 
are  as  follows: 

{a)  ZnCl2.6ZnO.6H2O; 

\b)  ZnCl2.3ZnO.4H2O; 

(^)    ZnCl2.9Zn0.3H,0. 
It  will  be  seen,  therefore,  that  the  general  formula  for  the 
three  is  ZnClinZnO.nHoO,  n  denoting  any  number. 

Method  of  Preparation.  -The  oxychloride 
is  prepared  from  a  powder  and  a  liquid,  as  in 

*Rollins's  process  for  making  the  oxymetaphosphate  is  as  follows: 
Dissolve  pure  zinc  in  C.  P.  nitric  acid  to  saturation,  then  evaporate 
to  dryness,  pack  in  a  crucible,  and  heat  till  no  more  fumes  are 
given  off.  Break  up  the  crucible  and,  after  separating  the  oxide  of 
zinc,  pulverize  it  to  a  very  fine  powder. 

Take  a  pure  solution  of  orthophosphoric  acid  (Section  266-1)  which 
can  easily  be  obtained  of  a  strength  of  sixty  per  cent.;  evaporate  it 
in  a  platinum  evaporating  dish  till  white  fumes  come  off.  Then 
heat  it  to  bright  redness  to  be  sure  that  it  is  all  converted;  cool,  and 
make  into  a  thick  syrup.  To  make  the  filling,  mi.K  the  powder  and 
fluid  in  suitable  proportions. 

Slow-setting  cements  are  less  durable  than  those  which  set  more 
rapidly  The  powder  should  be  worked  into  the  acid  gradually 
until  the  mass  is  stiff,  the  chief  point  being  not  to  add  too  much 
powder  at  a  time. 


INORGANIC   CHEMISTRY  ]^32 

the  case  of  the  oxyphosphate.  The  powder  is 
oxide  of  zinc,  and  the  Hquid  a  solution  of  zinc 
chloride  in  distilled  water  * 

Properties  ajtd  uses:  zinc  oxychloride  is  a  white  sub- 
stance, plastic  when  first  mixed,  but  rapidly  hardening 
with  age. 

It  is  used  in  dentistry  for  filling,  "lining,"  and  restoring 
color  to  discolored  teeth. 

203.  Zinc  Oxysulphate.— 

Theoretical  constitution:  the  mixture  used  in  dentistry 
under  this  name  is  composed  of  a  powder,  consisting  of 
one  part  of  calcined  zinc  sulphate  to  two  or  three  parts  of 
calcined  zinc  oxide.  Dissolved  in  a  solution  containing 
gum  arabic  and  a  little  sulphite  of  lime,  it  forms  a  plastic 
mass  soon  setting  and  very  dense  when  hard.     (Flagg). 

Uses  in  dentistry:  zinc  oxysulphate  is  used  in  dentistry 
as  an  adjunct  to  filling  materials. 

204.  Other  compounds  of  zinc. — 

Zinc  sulphate,  ZnSO^,  yW/d:  white  vitriol,  white  cop- 
peras, Zirici  Sulphas.  Occurs  in  small,  colorless,  trans- 
parent, efflorescent  crystals,  often  mistaken  for  Epsom 
salt,  astringent,  emetic,  irritant  poison.  Freely  soluble  in 
water,  insoluble  in  alcohol.  Disagreeable,  metallic,  styp- 
tic taste.  Made  by  dissolving  zinc  in  sulphuric  acid: 
Zn  +  H,S04  =  ZnSO^  +  H,. 

♦Various  methods  of  preparing  the  oxychloride  have  been  sug- 
gested and  as  the  zinc  chloride  is  7>ery  soluble  in  water  various 
strengths  of  solution  have  been  used,  such  as  1  part  to  2  of  water, 
equal  parts,  etc.,  etc.  According  to  Feichtinger  {Ditigler  s  Pol. 
Joitmal)  a  good  method  is  to  add  3  parts  of  zinc  oxide  and  1  part 
glass  powder  to  50  parts  of  a  solution  of  zinc  chloride  of  specific 
gravity,  1.5  to  1.6  to  which  is  further  added  1  part  of  borax  dissolved 
in  the   smallest  possible  quantity  of  water. 

Flagg  heats  oxide  of  zinc  with  borax,  adds  gradually  more  cal- 
cined oxide  of  zinc,  and  finally  mixes  with  the  zinc  chloride  solution. 


132  DENTAL   CHEMISTRY. 

Zinc  iodide,  Zniz  =  318.1.  Official  name,  Zinci  lodi- 
dum.  Made  by  digesting  granulated  zinc  30  Gm.  (465 
grains)  iodine  100  Gm.  (1550  grains)  water  200  C.  c. 
{6}{  fluid  ounces)  until  colorless  and  free  from  odor  of 
iodine,  subsequently  filtering  through  asbestos  or  pow- 
dered glass  and  evaporating  filtrate  rapidly  to  dryness  at 
moderate  heat.  Zinc  iodide  is  a  white,  granular  substance, 
very  readily  soluble  in  alcohol  and  in  water. 

Zinc  iodo-chloride  has  also  been  used  in  dentistry. 

Toxicology  of  zinc  compounds:  the  general  antidotes 
are  alkaline  carbonates,  as  sodium  carbonate;  white  of  egg, 
soap  and  water,  and  mucilaginous  drinks. 

205.    Cadmium. — 

Symbol:  Cd.  Latin  name:  Cadmium.  Equivalence: 
II.  Specific  gravity:  8.69.  Atomic  weight:  112.  Mole- 
cule composed  of  one  atom.  Revised  atomic  weight: 
1 1 1.835.  Electric  state'.  +•  Fusiftg  point:  442°  F. 
Length  of  bar,  etc.:  1.0031;  (first  in  rank,  most  expansi- 
ble). Wt.  of  cubic  ft.  in  lbs.:  542.5.  Tenacity:  greater 
than  tin.  Malleability,  Ductility:  flexible,  malleable,  and 
ductile.  CoTtductifig  power  {elQCtriciiy):  somewhat  lower 
than  zinc.  Resistance  to  air:  gradually  tarnishes  in  air; 
stained  yellow  by  sulphuretted  hydrogen.  Solubility: 
soluble  in  nitric  acid,  in  dilute  hydrochloric,  and  sul- 
phuric, but  not  in  caustic  alkalies.  Direct  combinations: 
oxygen,  chlorine,  sulphur.  Color  and  appearance:  like 
tin;  white  tinged  with  blue;  lustrous.  Structure:  crystal- 
izes  in  regular  octahedrons  on  cooling.  Consistence: 
harder  than  tin;  not  so  hard  as  zinc;  soft  enough  to 
mark  paper.  Compounds:  cadmium,  as  cadmium  sul- 
phate.    Alloys:    fusible   metal, amalgam  alloys. 

Occurrence:  cadmium  often  accompanies  zinc  in  its 
ores,  and  occurs  as  an  impurity  in  commercial  zinc.  It  is 
found  in  small  quantities,  not  over  2  or  3  per  cent.,  in  ores 
of  zinc.     It  occurs  most  abundantly  as  sulphide. 


INORGANIC    CHEMISTRY,  133 

Preparation:  the  metal  is  obtained  by  converting  the 
sulphide  into  oxide  by  heat,  and  then  reducing  this  with 
coal  or  charcoal. 

Uses  in  dentistry:  cadmium  is  a  constituent  of  easily 
fusible  alloys.  It  resembles  tin  in  color  and  appearance, 
and  creaks  like  the  latter  when  bent.  It  is  unalterable  in 
the  air.     It  has  been  used  in  dental  amalgam  alloys. 

206.     Compounds  of  Cadmium. 

Cadmium  Sulphate:  3(CdS04).  8H2O.  Obtained  by 
dissolving  metallic  cadmium,  its  oxide,  or  carbonate  in 
sulphuric  acid;  if  metallic  cadmium  is  used,  a  little  nitric 
acid  is  added  to  hasten  the  reaction,  and  afterwards 
driven  off  by  evaporation.  Cadmium  sulphate  occurs  in 
form  of  colorless,  transparent  crystals,  resembling  sul- 
phate of  zinc.  In  dentistry  it  has  been  used  in  various 
injections  and  lotions.  It  is  poisonous.  Percentage  of 
cadmium,  43.74. 

207.    Lead. 

Symbol:  Pb.  Latin  nainf.  Plumbum.  Equivalence'.  II 
and  IV.  Specific  gravity:  1 1.33  to  11.39.  Atomic  weight'. 
206.5.  Revised  atomic  weight:  206.4710.  Electrical  state'. 
+.  Fusing  point:  617°  F.  Length  of  bar,  etc.:  1.0028  (3d 
rank,  cadmium  =  i,  most  expansible).  Wt.  of  cubic  ft. 
in  lbs.:  709.2.  Tensile  strength:  0.8  to  1.5.  Relative 
tenacity:  i  (lowest  in  rank).  Malleability:  6;  (6th  rank). 
Ductility:  10;  (lOth  rank).  Conducting  power  (heat): 
9;  (9th  rank).  Conductiiig power  {^&\&z\x\Q\\.y\.  83;  (silver 
=  1000);  (lOth  rank).  Resistance  to  air,  etc.:  soon  tar- 
nishes; corroded  by  air  in  presence  of  carbonic  acid.  Dis- 
colored by  sulphuretted  hydrogen.  Solubility:  soluble  in 
dilute  nitric  acid;  attacked  by  hot  sulphuric.  Direct 
combinations:  oxygen,  chlorine,  bromine,  iodine,  sulphur. 
Amalgamates  readily.  Color  and  appearance:  bluish-white, 
brilliant.  Structure:  crystallizes  in  regular  octahedrons, 
or  in  pyramids  with  four  faces.     Consistence:  soft,   leaves 


134  DENTAL   CHEMISTRY. 

mark  on  paper.  Compounds',  mostly  plumb/r,  so-called, 
Pb".  Alloys',  solder,  type  metal,  pewter,  fusible  metal; 
has  affinity  for  platinum  and  palladium. 

Occurrence:  lead  occurs  in  nature  chiefly  as 
galena  or  galenite,  which,  like  cinnabar,  is  a 
sulphide,  PbS;  lOO  parts  of  the  pure  ore  con- 
tain 86>^  of  lead.  Another  ore  is  white-lead 
ore  or  carbonate  of  lead.  Galena  is  found  in 
Great  Britain,  Spain,  Saxony,  and  the  United 
States.  White  lead  ore  is  found  in  the  valley 
of  the  Mississippi;  in  Australia,  an  ore  called 
Ang-lesite,  which  is  a  sulphate  of  lead,  is  found. 
Other  ores  are  crocoisite  (a  chromate),  Wul- 
fenite  (a  molybdate),  and  pyromasphite  (a 
phosphate). 

Preparation  :  galena  is  roasted,  during: 
which  process  two  products,  lead  oxide  and 
lead  sulphate,  are  formed;  the  two  products 
thus  obtained  are  then  strongly  heated  in  a 
reverberatory  furnace,  metallic  lead  and  sul- 
phurous oxide  being  formed. 

Dental  uses:  lead  alloys  with  other  metals, 
and  is  an  ingredient  of  various  solders:  com- 
mon solder  is  50  parts  lead  and  50  parts  tin. 
Lead  is  used  in  dentistry  chiefly  in  making 
counter-dies.  [Thin  sheets  of  it  are  used 
for  making  patterns  by  which  gold  or  silver 
plate  is  cut,  so  that  bits  of  it  may  be  found  in 
the  dentist's  gold  drawer;  a  very  small  amount 
of  it  will  greatly  impair  the  ductility  of  gold]- 


INORGANIC   CHEMISTRY.  135 

Compounds  of  lead:  oxides  of  lead  are  used 
as  coloring  matters  for  artificial  teeth.  Plum- 
bic peroxide  (dioxide)  PbOa,  is  a  chocolate- 
brown  or  puce-colored  powder,  which  gives  off 
its  oxygen  on  being  heated. 

Litharge  is  plumbic  oxide,  PbO,  prepared  by  heating 
melted  lead  in  a  current  of  air.  It  is  pale  yellow  or  orange 
yellow  in  color.  By  oxidizing  litharge  in  a  current  of  air 
and  cooling  slowly,  a  substance  used  in  the  arts  as  a  pig- 
ment and  called  plumbic  meta-plumbate,  Pb^Pb^^'Os,  or 
PbjOa,  is  formed.  The  plumbic  plumbates  form  the  sub- 
stances known  as  red-leads. 

208.  Compounds  of  Uranium.— 

An  oxide  of  uranium  is  used  by  dentists  as  a 
coloring  matter  for  artificial  teeth.*  Its  formula 
is  U2O3,  uranic  oxide,  or  uranyl  oxide  as  it  is 
sometimes  called.  Uranic  nitrate  heated  in  a 
glass  tube  till  it  decomposes  yields  pure 
uranic  oxide  in  the  form  of  a  yellowish  pow- 
der. 

Another  oxide  of  uranium  is  uranous  oxide,  UO,  a 
brown  powder. 

209.  Copper. 

Symbol:  Cu.  Latin  name'.  Cuprum.  Equivalence'. 
(Cu2)^^  and  II.  Specific  gravity:  8.914  to  8.952.  Atomic 
weight:  63.2.  Revised  atojnic  weight:  63.173.  Electrical 
state:  +.  Fusing  point:  1996°F.  Lejtgth  of  bar,  etc.: 
1.0017;    (7th  in  rank).     Weight  of  cubic  foot  in  lbs.:  558.1. 

*Rollins  uses  such  oxides  as  contain  the  most  oxygen,  that  is, 
uranic  rather  than  uranous,  plumbic  dioxide  rather  than  protoxide, 
etc.,  etc.,  because  the  coloring  matters  sometimes  lose  oxygen  in 
firing. 


136  DENTAL   CHEMISTRY. 

Tensile  strength:  13  to  15.  Tenacity.  18,  (Lead  =  i); 
(3d  rank).  Malleability :  3;  (3d  rank).  Ductility:  5;  (5th 
rank).  Conducting  power  {\iQ-dX)\  y,  {"i^^raxsk.^.  Conducting 
/^zf^;' (electricity):  999,  (Silver  :=  1000);  (2d  rank).  Re- 
sistance to  air,  etc.:  in  moist  air  becomes  coated  with  green 
carbonate.  Tarnished  by  sulphuretted  hydrogen.  Solu- 
bility: soluble  in  hot  mineral  acids,  and  attacked  by 
vegetable  acids  in  presence  of  air  and  moisture.  Attacked 
by  chlorine  and  nitric  acid,  and  by  sulphur  when  heated; 
slowly  attacked  by  weak  acids,  alkalies,  and  saline  solu- 
tions. Direct  cotnbinations :  sulphur,  chlorine,  bromine, 
iodine,  silicon,  and  various  metals  at  red  heat.  Color 
and  appearance :  lustrous,  flesh  red.  Structure:  crystal- 
lizes in  isometric  forms,  Consistetice :  somewhat  softer 
than  iron.  Compounds:  cuprous  (Cuj)"  and  cupric. 
Alloys:  Aich's  metal,  aluminium  bronze,  arguzoid,  bell- 
metal,  brass,  Britannia  metal,  bronze,  Dutch-metal, 
electrum,  German  silver,  gold  coinage,  gun-metal, 
Muntz's  metal,  pewter,  silver  coinage,  some  solders, 
speculum  metal,  sterro-metal,  tutenag. 

Occurrence:  native  copper  exists  near  Lake 
Superior;  in  its  ores  it  is  found  as  oxide,  sul- 
phide, carbonate,  and  in  combination  with  sul- 
phide of  iron,  forming-  copper  pyrites.  The 
metal  is  found  in  England,  Sweden,  Saxony, 
Siberia,  Australia,  Chili,  and  in  the  United 
States. 

Preparation:  the  ores  are  first  roasted  in  air, 
then  with  silica  fluxes  and  carbon,  and  finally 
a  substance  called  copperstone  is  obtained, 
which  contains  both  oxide  and  sulphide  of  cop- 
per.     By  repeating  the  roasting  and.  heating. 


INORGANIC   CHEMISTRY.  137 

the  oxide  reacts  on  the  sulphide,  and  metalhc 
copper  is  obtained. 

Pure  Copper  may  be  obtained  by  electroly- 
sis. A  solution  of  cupric  sulphate  is  used,  and 
the  neg"ative  wire  of  a  battery  attached  to  a 
copper  plate  which  is  immersed  in  the  solution. 
Pure  copper  is  deposited  on  the  plates,  and  may 
easily  be  stripped  off. 

Use  in  dentistry:  copper  is  used  as  a  con- 
stituent of  some  dental  amalg"am  alloys."^ 

Alloys  of  Copper : 
•  Babbitt  Metal  is  an  alloy  of  copper,  3  parts;  antimony, 
I  part;  tin,  3  parts.  The  copper  is  fused  and  then  anti- 
mony and  tin  are  added  to  it.  It  melts  at  a  moderately 
low  heat;  contracts  but  little;  is  brittle,  but  maybe  render- 
ed less  so  by  adding  tin. 

210.  Brass  is  an  alloy  of  copper  and  zinc.  Common 
brass  is  made  of  66.6  parts  copper  and  33.3  zinc;  best 
brass,  71.4  copper  to  28.6  zinc.  Yellow  brass  is  60  copper 
to  40  zinc.     Brass  melts  at  1869°  F. 

211.  Bell  metal  is  an  alloy  of  6  parts  copper  to  2 
parts  tin;  some  varieties  are  78  copper  to  22  tin.  Cannon 
metal  is  90  copper  to  10  of  tin. 

212.  Bronze  is  an  alloy  of  copper  and  tin.  Aluminium 
bronze,  900  parts  copper  to  100  of  aluminium.  The  lat- 
ter has  been  used  for  the  under  layer  of  teeth  plates,  and 
is  said  to  be  free  from  injurious  oxidation  and  to  be  more 
easily  manipulated  than  gold  alloys  or  silver.  It  may  be 
stamped  and  pressed,  almost  as  easily  as  pure  silver,  while 
possessing  the  elasticity  of  steel.  Its  melting  point  is 
higher  than  that  of  pure  gold,  so  that  it  may  be  made  red 
hot  without  danger  of  melting,  and  can  be  manipulated 

*See  Copper  Amalgam  under  Mercury. 


138  DENTAL   CHEMISTRY. 

with  hard  solder.  Sauer  solders  it  with  from  14  to  16 
carat  red  gold.  Aluminium  bronze  is  one-half  lighter 
than  12  carat  silver  and  almost  half  the  weight  of  14  carat 
gold.  It  oxidizes,  superficially  only,  in  the  mouth;  it  is 
affected,  superficially,  by  a  i  in  1,000  solution  of  corrosive 
sublimate,  but  not  by  carbolic  acid. 

213.  Gold  aluminium  bronze  oxidizes  more  readily,  is 
softer,  and  not  so  elastic. 

214.  Phosphor  bronze  is  copper,  combined  with  from 
3  to  15  per  cent,  of  tin,  and  from  ^  to  2j^  per  cent,  of 
phosphorus. 

215.  Speculum  metal  is  an  alloy  of  copper  and  tin; 
66.6  copper  and  33.3  tin. 

216.  Compounds  of  Copper. — 

Cupric  Sulphate:  CuSO^,  5H2O.  Known  as  sulphate 
of  copper,  blue  vitriol,  Roman  vitriol,  blue  stone,  blue 
copperas,  vitriol  of  copper.  Official  name,  Cupri  Sulphas. 
Made  on  a  large  scale  by  dissolving  copper  in  sulphuric 
acid,  evaporating,  and  allowing  to  crystallize: 

Cu     +     2H2SO4     =     CuSO,     +     2H,0     +     SO2. 

Copper  sulphuric  acid  cupric  water  sulphurous 

sulphate  oxide 

It  occurs  in  the  form  of  blue,  prismatic  crystals,  efflor- 
escent, of  astringent,  metallic  taste,  soluble  in  4  parts 
water,  insoluble  in  alcohol.  In  dentistry  it  is  used  exter- 
nally, dissolved  in  ammonia,  as  an  astringent  and  styptic. 
it  is  poisonous;  antidotes:  milk,  white  of  egg  given  freely. 

217.  Mercury  (quicksilver). 

Symbol:  Hg.  Latin  name:  Hydrargyrum.  Equivalence : 
(Hg2)"andII.  Specific  gravity :  13.596.  Atomic  weight: 
199.7.  Molecule  composed  of  one  atom.  Revised  atomic 
weight:  199.7120.  Electrical  state:  +.  Fusing  point :  liquid 
at  ordinary  temperatures.  Boils  at  660°  F.  Length  of  bar 
total  expansion,  1.0180.  Malleable  at — 40"  F.  Resistance 
to  air,  etc.:  unaltered  in  air;  does  not  leave  streak  on  paper. 


INORGANIC   CHEMISTRY.  I39 

Solubility :  soluble  in  dilute  nitric  acid  and  hot  sulphuric; 
insoluble  in  hydrochloric  acid.  Direct  combinations:  dis- 
solves all  metals  but  iron  •  combines  directly  with  halogens 
and  sulphur.  CcL,  and  appearance :  opaque,  with 
metallic  lustre;  brilliant  silver- white.  Structure:  octahe- 
dral crystals  at — 40°  F.  Consistence:  liquid;  slightly 
volatile.  Compounds:  mercurous  (Hg2)"and  mercuric. 
Alloys:  amalgams.  Use  in  dental  amalgam  alloys:  mer- 
cury amalgamates  readily  with  gold,  zinc,  tin,  and  silver; 
also  with  copper,  platinum,  palladium,  and  cadmium. 

Occurrence  and  preparation:  mercury  is 
found  in  the  form  of  Cinnabar,  which  is  native 
mercuric  sulphide.  Large  quantities  of  it  are 
obtained  in  Cahfornia;  it  is  also  found  in 
Spain,  Austria,  Mexico,  Peru,  China,  Japan, 
Borneo.  Mercury  is  obtained  from  cinnabar, 
either  by  roasting  the  latter  or  by  heating  it 
with  lime,  which  combines  with  the  sulphur  of 
the  cinnabar,  while  the  metal  volatilizes  and  is 
condensed  in  suitable  coolers. 

The  equation  of  the  preparation  of  mercury 
is 

HgS        +        2O      =      Hg       +       SO2 

Mercuric  Oxygen.  Mercury.  Sulphurous 

sulphide.  oxide. 

Dental  uses:  amalgams.  Mercury  readily 
alloys  with  other  metals,  forming  combinations 
called  amalgams. 

This  property  of  mercury  may  be  readily 
shown  by  the  following  experiment:  clean  a 
copper  cent  with  a  little  nitric  acid,  wash  well 
with  water,  and  on  it  place  a  globule  of  mer- 


140  DENTAL  CHEMISTRY. 

cury;  the  latter  soon  covers  the  whole  surface 
of  the  cent,  giving-  it  a  white  color.  Heat  the 
cent  and  its  original  color  will  be  restored,  the 
mercury  volatilizing.  Many  of  the  alloys  of 
mercury  with  other  metals  are  soft  when  fresh- 
ly formed,  but  harden  with  time,  hence  their 
value  for  fillings. 

The  combinations  formed  are,  in  the  case  of  solid 
amalgams,  definite  compounds  in  which,  however,  there 
is  but  feeble  chemical  affinity  between  the  constituents. 
Liquid  amalgams  are  merely  solutions  of  the  various 
metals  in  mercury,  and  not,  as  a  rule,  definite  chemical 
compounds.  Many  liquid  amalgams  become,  however, 
after  a  time,  white,  solid,  and  crystalline.  There  is 
usually  little  or  no  contraction  in  volume,  but  in  the  case 
of  silver  and  copper  amalgams  there  is  considerable,  and 
in  tin  and  lead  slight,  though  perceptible.     (Watts). 

Amalgams  are  decomposed  by  heat. 
218.    The  methods  by  which  amalgamation 
may  be  made  to  take  place  are  as  follows: 

1.  Direct  contact  on  part  of  the  metal, 
either  as  a  solid  or  in  the  finely  divided  state, 
with  mercury,  either  at  ordinary  temperatures 
or  at  higher  temperatures.  Heat  is  evolved 
during  the  amalgamation. 

2.  Introduction  of  metallic  mercury,  or  of 
sodium-amalgam,  into  a  solution  of  a  salt  of  a 
metal. 

3.  Introduction  of  a  metal  into  a  solution  of 
a  salt  of  mercury. 

4.  Contact  of  a  metal  with  mercury  and 
addition  of  a  dilute  acid. 


INORGANIC   CHEMISTRY.  141 

In  the  last  two  cases  a  weak  electric  current 
is  sometimes  developed. 

Electricity  is  often  used  to  facilitate  the  union 
of  mercury  with  a  metal  precipitated  from  a 
solution  of  one  of  its  salts.  (See  Copf)er 
Amalgani). 

2 1 9.  Antimony  amalgam :  triturate  3  parts  heated  mer- 
cury with  I  part  fused  antimony;  or  triturate  2  parts  anti- 
mony in  a  mortar,  add  a  little  hydrochloric  acid,  and  gradu- 
ally drop  in  i  part  of  mercury.  The  amalgam  is  soft,  de" 
composed  by  contact  with  air  or  water,  and  the  anti- 
mony separates. 

Amalgams  containing  antimony  in  notable  quantity  are 
fine  grained,  plastic,  and  do  not  shrink,  but  are  excessively 
dirty  to  work.  Used  in  small  proportions  in  amalgams  it 
is  said  to  be  of  possible  value  in  controlling  shrinkage.* 

220.  Cadmium  amalgam:  cadmium  amalgamates  at 
ordinary  temperatures.  When  complete  saturation  takes 
place,  as  through  agency  of  sodium-amalgam  in  a  solution 
of  salt  of  cadmium,  a  compound  of  78.26  Hg  to  21.74  Cd 
is  formed,  having  for  its  formula,  therefore,  HgjCd,  and 
being  silver-white,  granular,  hard,  brittle,  heavier  than 
mercury,  and  in  octahedral  crystals.     (Watts). 

Cadviiian  amalgamates  easily,  sets  quickly,  and  resists 
sufficiently,  but  fillings  containing  it  gradually  soften  and 
disintegrate,  and,  if  there  is  a  large  proportion,  the  den- 
tine becomes  decalcified  and  stained  bright  orange-yellow 
from  formation  of  cadmium  sulphide. 

221.  Copper  amalgam :    there   are   various   processes 


*Dr.  Chase's  "  alcohol  tight "  amalgam  contains  nearly  five  per 
cent,  of  antimony.     (Weagant). 


142  DENTAL    CHEMISTRY. 

for  making  copper  amalgam.  Rollins,  Ames,  and  others 
make  it  by  electrolysis. 

Rollins's  method  is  as  follows:* 

Distilled  water,  five  gallons;  sulphate  of  copper,  enough 
to  saturate;  sulphuric  acid,  one  pound.  Mix,  filter,  and 
pour  into  a  wooden  firkin  with  wooden  hoops.  All  the 
chemicals  should  be  absolutely  pure.  Place  ten  pounds 
of  pure  mercury  in  a  glass  jar  and  immerse  in  the  copper 
solution.  To  the  zinc  plate  of  a  galvanic  battery  attach 
a  gutta-percha-covered  wire,  having  one  end  bare  for  about 
an  inch.  This  exposed  end  is  to  be  immersed  below  the 
level  of  the  surface  of  the  mercury.  Tie  granulated  pure 
copper  in  a  bag  and  hang  it  in  the  copper  solution,  con- 
necting with  a  wire  to  the  carbon  of  the  battery.  The 
battery  is  to  be  kept  in  action  till  the  mercury  has  ab- 
sorbed enough  copper  to  make  a  thick  paste.  Then 
remove  and  wash  thoroughly  in  hot  water  till  all  of  the 
sulphate  solution  has  been  removed.  Squeeze  out  the 
softer  amalgam  and  allow  the  remainder  to  harden.  When 
it  is  hard,  heat  it,  and  renew  the  squeezing  as  before.  This 
new  method  insures  an  amalgam  of  perfect  purity,  and  is 
simpler  tlTan  any  of  the  old  and  faulty  ways  in  use. 
Copper  amalgam  dissolves  rapidly  in  mouths  where  the 
saliva  is  acid,  and  in  this  way  serves  as  an  indicator  of  the 
condition  of  the  oral  fluids.  It  stains  teeth  in  a  certain 
proportion  of  cases,  particularly  when  teeth  have  lost 
their  pulps,  or  when  the  dentine  is  of  an  open  structure. 

A  battery  answers  for  home  manufacture,  but  on  a 
larger  scale  a  dynamo  should  be  used. 

Dr.  T.  H.  Chandler,  of  Boston,  has  described  to  me  the 
following  processes  for  making  copper  amalgam,  which  he 
calls  •'  No.  I  "  and  "  No.  2."  He  thinks  "  No.  i  "  an 
excellent  filling: 

♦Boston  Medical  and  Surgical  Journal,  February,  1886. 


INORGANIC   CHEMISTRY.  143 

No.  I, — To  a  hot  solution  of  sulphate  of  copper  add  a 
little  hydrochloric  acid,  and  a  few  sticks  of  zinc,  and  boil 
for  about  a  minute.  The  copper  will  be  precipitated  in  a 
spongy  mass.  Take  out  zinc,  pour  off  liquor,  and  wash 
the  copper  thoroughly  with  hot  water.  Pour  on  the  mass 
a  little  dilute  nitrate  of  mercury,  which  will  instantly 
cover  every  particle  of  the  copper  with  a  coating  of  the 
mercury.  Add  mercury  two  or  three  times  the  weight  of 
the  copper,  triturate  slightly  in  a  mortar  and  finish  by 
heating  the  mixture  a  few  moments  in  a  crucible. 

No.  2. — Take  finely  divided  copper  (copper  dust)  ob- 
tained by  shaking  a  solution  of  sulphate  of  copper  with 
granulated  tin.  The  solution  becomes  hot,  and  a  fine 
brown  powder  is  thrown  down.  Of  this  powder  take  20, 
30,  or  36  parts  by  weight  and  mix  in  a  mortar  with  sul- 
phuric acid,  1.85  specific  gravity,  to  a  paste,  and  add  70 
parts  of  mercury  with  constant  stirring.  When  well  mixed, 
wash  out  all  traces  of  acid  and  cool  off.  When  used,  heat 
to  1300°  F;  it  can  be  kneaded,  like  wax,  in  a  mortar. 

While  in  this  plastic  state,  it  is  an  excellent  solder  for 
metals,  glass,  etc.,  used  by  applying  it  to  surfaces  to  be 
joined,  pressing  hard  together  and  allowing  it  to  set. 

Weagaiit's  process  for  making  copper  amalgam  is  as 
follows: 

Nearly  fill  a  vessel  with  a  solution  of  copper  sulphate, 
one  part  of  a  saturated  solution  to  two  or  three  parts 
water.  Pour  into  it  enough  mercury  to  cover  well  the 
bottom  of  the  glass,  and  stand  a  clean  strip  or  plate  of 
iron  in  the  mercury,  allowing  the  end  to  project  above  the 
glass.  Pure  precipitated  copper  in  finely  divided  state 
will  at  once  become  deposited  on  the  iron,  and  the  mercury 
will  gradually  unite  with  the  copper,  creeping  up  the  iron 
until  the  whole  surface  is  covered  with  a  film  of  amalgam. 
If  the  iron  is  placed  for  a  moment  in  a  weak  solution  of 
sulphuric  acid  just  before  being  immersed  in  the  copper 
bath,  amalgamation  takes  place  more  rapidly. 


144  DENTAL   CHEMISTRY 

It  must  be  allowed  to  stand  undisturbed  until  the  change 
in  the  color  of  the  solution  shows  that  all  the  copper  is 
precipitated.  Then  with  a  siphon  draw  off  the  liquid 
and  renew  the  sulphate  of  copper.  This  proceeding  may 
be  repeated  as  long  as  the  mercury  takes  up  the  copper. 
When  all  the  mercury  has  become  amalgamated,  scrape 
off  whatever  amalgam  adheres  to  the  strip  of  iron,  pour 
off  the  liquid,  and  turn  the  mass  of  amalgam  into  a  mor- 
tar. Rub  and  wash  it  thoroughly,  allowing  a  stream  of 
water  to  fall  upon  it  from  a  tap,  cleaning  out  all  the  free 
metallic  copper  and  scales  of  oxide  of  iron.  As  soon  as 
it  is  as  clean  as  it  can  be  made,  place  it  in  a  chamois  skin 
and  squeeze  out  the  surplus  mercury.  Then  the  washing 
and  grinding  in  the  mortar  must  be  repeated  until  the 
mass  again  becomes  soft,  when  more  mercury  can' be  re- 
moved. The  greatest  care  must  be  taken  to  remove  all 
the  little  scales  and  grains  of  iron,  or  the  amalgam  will 
be  dirty  to  work,  and  the  best  results  from  it  cannot  be 
obtained.  When  the  amalgam  has  been  well  worked  and 
all  the  mercury  possible  squeezed  out,  heat  it  gently  in  an 
iron  vessel.  The  first  time  this  must  be  done  carefully, 
as  steam  from  water  which  is  retained  in  it  becomes 
generated,  and  the  mass  will  explode,  flying  in  all  direc- 
tions. When  the  amalgam  begins  to  get  soft,  rub  in  a 
mortar,  and  again  squeeze  out  mercury.  This  heating, 
rubbing,  and  squeezing  must  be  repeated  again  and  again, 
until  very  little  mercury  can  be  removed  and  the  amalgam 
is  found  to  set  instantly,  and  become  very  hard.  It  may  then 
be  made  into  little  sticks  or  pellets,  and  laid  away  for  use. 
To  use  it,  place  the  quantity  required  in  an  iron  spoon 
and  heat  it  over  a  flame'  until  mercury  begins  to  show 
like  sweat  upon  the  surface.  Then  crush  and  grind  the 
mass  in  a  small  mortar,  and  work  together  in  the  hand. 
If  too  soft,  squeeze  in  a  piece  of  chamois  skin,  using  a 
pair  of  pliers  if  necessary.      One  soon  learns  how  soft  or 


INORGANIC   CHEMISTRY.  145 

dry  to  make  it  in  order  to  get  the  best  results.  Do  not 
throw  away  any  of  the  scraps  remaining,  as  they  may  be 
used  over  and  over  again  an  indefinite  number  of  times, 
seeming  to  improve  by  age.  Be  careful  not  to  heat  too 
much,  as  some  of  the  mercury  volatilizes,  leaving  pure 
copper,  which  becomes  oxidized  by  the  heat  and  makes 
the  amalgam  dirty. 

A  weak  solution  of  sulphate  of  copper  is  used  instead 
of  the  saturated  solution,  as  the  precipitate  is  much  finer 
and  the  amalgam  requires  less  rubbing  to  bring  it  to 
shape. 

Copper  amalgam  is  composed  of  pure  copper  and  pure 
mercury  in  variable  proportions.  The  less  mercury  it 
contains  the  more  quickly  it  sets  and  the  harder  it  be- 
comes. When  properly  made  it  is  exceedingly  pleasant 
to  work,  fine-grained  and  plastic,  and  sets  either  slowly  or 
rapidly,  as  we  desire  it  and  are  pleased  to  prepare  it.  It 
becomes  very  hard — harder  in  fact  than  any  amalgam 
made  from  alloys.  It  is  not  known  to  shrink  or  expand 
in  the  least  degree.  It  does  not  ball  up  nor  change  its 
shape  in  any  way  during  the  setting  or  afterwards,  and 
finally,  instead  of  having  any  injurious  effect  upon  the 
teeth  or  surrounding  tissues,  it  is  decidedly  beneficial  to 
them,  acting  as  an  antiseptic  or  germ  destroyer.  But,  al- 
though it  does  not  cause  discoloration  of  the  teeth,  the 
filling  itself  will  quickly  and  emphatically  become  black 
— very  black — upon  the  surface.  It  should  always  be 
carefully  polished  when  hard,  for,  although  polishing  does 
not  prevent  its  turning  black,  it  is  a  polished  black,  and 
not  so  disagreeable  and  dirty  looking  as  when  left  with  a 
rough  surface.     (Weagant). 

The  sulphide  of  copper  formed  by  the  action  of  the 
sulphuretted  hydrogen  of  the  mouth  on  the  copper  of  the 
amalgam  is,  according  to  Tomes,  readily  converted,  on 
exposure  to  air  and  moisture,  into  copper  sulphate,  hence 


146  DENTAL    CHEMISTRY. 

it  is  almost  certain  that  the  latter  is  formed  on  the  ex- 
posed surface  of  the  filling,  Cupric  sulphate  is  freely 
soluble,  and  hence  is  likely  to  permeate  the  dentine. 
Sulphides  of  the  other  metals  are  not  so  readily  converted 
into  soluble  salts,  hence  will  not  permeate  the  dentine  so 
thoroughly.* 

222.  Gold  amalgam:  gold,  in  leaf  or  filings,  amalga- 
mates readily  with  mercury  at  ordinary  temperatures. 
For  rapid  amalgamation,  heat  should  be  used,  and  the 
gold  be  in  the  finely  divided  state. 

Gold  added  to  amalgams  of  tin  and  silver  is  valuable  in 
that  it  controls  shrinkage,  balling,  and  discoloration, 
facilitates  setting,  and  adds  to  edge-strength.  Amalgams 
containing  it  are  smoothly  and  easily  worked.  Some 
dentists  use  amalgams  containing  a  very  large  proportion 
of  gold. 

223.  Palladium  amalgam: — 

Palladium  has  been  recently  brought  to  notice  as  form- 
ing with  three  times  its  weight  of  mercury  a  desirable 
dental  amalgam,  especially  useful  in  the  sixth-year  molars 
of  young  patients.f 

Some  care  is  necessary  in  the  mixing,  as  palladium 
forms  a  true  chemical  compound  with  mercury,  and  the 
action  is  so  intense  that  under  certain  circumstances  an 
■explosion  may  result.  Palladium  fillings  become  black, 
but  do  not  discolor  the  tooth-substance. 

The  amalgam  sets  with  such  great  rapidity  that  it  is 
necessary  to  mix  it  quite  soft  in  order  to  make  a  filling 


♦Copper  sulphate  has  been  successfully  used  abroad  as  a  preserva- 
tive for  telegraph  poles. 

fDr.  E.  A.  Bogue  has  used  palladium  amalgam.  In  the  proportion 
of  seventy-five  per  cent,  mercury  to  twenty-five  per  cent,  of  pure  pre- 
cipitated palladium  the  expense  is  greatly  reduced. 


INORGANIC   CHEMISTRY  147 

before  it  is  too  hard  to  use.*      It  must   be   worked  very 
quickly,  and  with  heated  instruments. 

224.  Platinum  amalgam:  metallic  platinum  does  not 
unite  readily  with  mercury.  Spongy  platinum  unites  with 
mercury,  when  triturated  in  a  warm  mortar  with  the  lat- 
ter, or  in  contact  with  acetic  acid;  or  sodium-amalgam 
containing  i  percent,  sodium,  if  introduced  into  a  solution 
of  platinic  chloride,  will  form  an  amalgam  of  silvery  ap- 
pearance. The  amalgam  containing  lOO  parts  mercury, 
to  15.48  platinum,  has  asp.  gr.  of  14.29,  and  has  metallic 
lustre  when  rubbed;  100  mercury  to  21.6  platinum  is  a 
dark  gray  solid;  lOO  mercury  to  34.76  platinum  is  of  14.69 
sp.  gr.,  dark  gray,  but  of  no  lustre;  lOO  mercury  to  12 
platinum  is  bright,  but  soft  and  greasy.  The  solid  amal- 
gam containing  the  most  mercury  is  probably  PtHgg. 
Mercury  exposed  for  some  time  to  the  action  of  platinic 
chloride  forms  a  thick,  pasty  amalgam. 

In  general,  it  may  be  said  that  an  amalgam  of  mercury 
and  platinum  alone  does  not  harden  well.f 

Platinum,  according  to  Essig,  is  of  value  only  when  com- 
bined with  tin,  silver,  and  gold,  with  the  proper  amount 
of  mercury;  under  such  circumstances,  it  seems  to  confer 
on  the  alloy  the  property  of  almost  instantly  setting,  and 
of  being  much  harder.  According  to  Fletcher,  the  amal- 
gam should  be  used  immediately,  before  the  platinum 
and  mercury  have  time  to  set. 

225.  Silver  amalgam:  amalgamation  takes  place 
quickly,  if  the  silver  is  in  thin  plates,  or  in  powder,  and 
dropped  at  red  heat  into  heated  mercury.  The  amalgam 
varies  according  to  circumstances  of  formation,  composi- 
tion,   etc.,    and  is  soft,  or  crystalline,  or  granular.     The 

*Dr.  Chandler  mixes  gold  in  large  proportion  in  order  to  render 
the  palladium  more  tractable. 

tDr.  Ames,  of  Chicago,  has  prepared  platinum  amalgam  by 
electrolysis. 


148  DENTAL    CHEMISTRY. 

amalgam  most  readily  formed  has  for  its  formula  AgHg. 
[Amalgams  of  mercury  and  silver  are  said  by  Watts  to 
contract  considerably,  but  by  others  to  expand.  The 
proportions  are  undoubtedly  of  importance]. 

Amalgams  composed  of  silver  and  mercury  alone  tend, 
when  used  as  fillings,  to  change  their  shape.  But  silver 
used  in  connection  with  other  metals  is  the  most  import- 
ant element  in  a  good  amalgam  for  filling  teeth.*  Silver 
forms  silver  sulphide  in  contact  with  the  sulphuretted 
hydrogen  of  the  mouth,  and  both  tooth  and  filling  are 
blackened  in  consequence;  but  the  tendency  is  toward 
preservation  of  the  tooth. 

226.  Tellurium  and  mercury  are  said  to  unite  directly, 
forming  a  tin-colored  amalgam. 

227.  Tin  amalgam:  made  readily  and  quickly  by 
pouring  mercury  into  melted  tin,  but  readily  enough  by 
mixing  the  filings  with  mercury  at  ordinary  temperatures. 
Tin  amalgam  has  a  white  color,  and,  if  there  is  not  too 
much  mercury,  occurs  in  form  of  a  brittle,  granular  mass 
of  cubical  crystals.  In  most  cases  there  is  condejisation^ 
but  in  the  amalgam  composed  of  i  part  tin  to  2  mercury 
(melted  and  by  volume)  the  condensation  is  scarcely 
perceptible. 

Amalgams  composed  of  mercury  and  tin  alone  do  not 
harden  sufficiently.  In  an  alloy  with  other  metals,  tin  is 
valuable  in  that  it  facilitates  amalgamation,  prevents  dis- 
coloration, and  diminishes  conductivity. 

228.  Zinc  amalgam :  usually  made  by  cooling  melted 
zinc  to  as  lo,w  a  temperature  as  possible  without  letting  it 
solidify,  then  pouring  in  mercury  in  a  fine  stream,  and 
stirring  constantly. 

Amalgams  of  mercury  and  zinc  alone  are  not  common- 

*Silver  is  the  largest  comf>onent  of  most  of  the  reliable  amalgam 
alloys  on  the  market. 


INORGANIC   CHEMISTRY.  149 

ly  used.  Added  to  alloys  of  tin  and  silver  in  as  small 
proportion  as  one  per  cent.,  zinc  controls  shrinkage,  adds  to 
the  whiteness  of  the  filling,  and  tends  to  maintain  color.* 

229.  Dental  amalgam  alloys :  it  will  readily  be  per- 
ceived from  a  study  of  common  amalgams  that  but  few 
of  them  would  be  of  service  to  the  dentist.  On  the  other 
hand  combinaiions  of  metals,  often  first  melted  in  tin, 
brought  about  through  the  agency  of  mercury — that  is, 
amalgams  of  several  metals  at  once, — alloy  amalgams — have 
been  found  very  useful,  so  that  now  large  quantities  are 
used.  Amalgams  for  dental  purposes  are  chiefly  com- 
posed of  tin  and  silver,  in  different  proportions,  of  which 
Townsend's  alloy  of  6o  tin  to  40  silver  may  be  taken  as 
the  type.  Some  dental  amalgam  alloys,  as  Hardman's 
and  Lawrence's,  contain  copper  in  addition  to  tin  and 
silver;  some  contain  zinc,  gold,  etc.  The  list  of  metals 
used  in  the  dental  amalgam  alloys  comprises  tin,  silver, 
copper,  zinc,  gold,  platinum,  cadmium,  antimony, 
palladium.  The  so-called  "gold  and  platina  alloys," 
according  to  Flagg,  contain  50  per  cent,  of  tin,  more  than 
40  of  silver,  and  from  2  to  7  of  gold  and  platinum. 

[In  regard  to  the  average  proportions  of  tin  and  silver, 
Flagg  finds  40  tin  to  60  silver  the  best  working  formula, 
modified  by  additions  of  copper,  gold,  and  zinc]. 

230.  Qualities  desirable  in  dental  amalgam  a;lloys: 
strength  and  sharpness  of  edge,  freedom  from  admixture 
with  any  metal  favorable  to  the  formation  of  soluble  salts 
of  an  injurious  character  in  the  mouth,  capability  of 
maintenance  of  color  and  shape,  and  non-liability  to 
undue  expansion.  N.  B. — Absolute  freedom  from  dis- 
coloration can  not  often  be  obtained,  nor  is  it  always 
desirable,  according  to  Flagg. 

♦Chandler's  experiments  with  zinc  lead  him  to  prefer  sifting  in  a 
small  percentage  oipure  zinc  dust  at  the  "mix  "  rather  than  melt- 
ing it  with  the  other  ingredients  of  an  amalgam  alloy. 


150  DENTAL   CHEMISTRY. 

231.  Discoloration  of  amalgam  fillings:  the  forma- 
tion of  sulphides,  due  to  the  sulphuretted  hydrogen 
resulting  from  the  decomposition  of  the  food,  is  the  main 
cause  of  the  discoloration  of  amalgam  fillings;  black  dis- 
coloration is  found  in  fillings  containing  silver  or  copper; 
yellowish  discoloration  in  those  containing  cadmiian. 
According  to  Essig,  it  is  not  safe  to  suppose  that  a  metal 
not  of  itself  blackened  by  sulphuretted  hydrogen — as 
gold  or  platinum — will  secure  the  same  immunity  to  alloys 
containing  silver  and  mercury.  It  has  been  noticed  that 
plugs,  which  apparently  exclude  the  passage  of  a  solution 
of  indigo  or  ink,  will  show  peripheral  discoloration  when 
exposed  to  the  action  of  a  sulphuretted  hydrogen  solu- 
tion, though  the  surface  directly  exposed  to  the  action  of 
the  sulphur  was  but  slightly  clouded.*     (Essig). 

Discoloration  of  gold  fillings:  Chandler  takes  the 
ground  that  the  discoloration  of  gold  in  the  mouth  is  due 
to  oxidation  of  the  steel  worn  from  pluggers. 

232.  Compounds  of  Mercury:— 
Mercuric  chloride  or  corrosive  sublimate: 

Synonyms:  corrosive  chloride,  bichloride  of 
mercury,  "  oxymuriate  "  of  mercury,  perchlor- 
ide  of  mercury,  deuto-chloride  of  mercury, 
Hydrargyri  Perchloridum.  Official  name, 
Hydrargyri  Chloridum  Corrosivum. 

Theoretical  constitution:  HgCla  or  mercuric 
chloride.  Mercury  as  a  dyad.  The  molecule 
is  composed  of  one  atom  of  mercury  to  two  of 
chlorine;  by  weight,  mercury  200  parts,  chlor- 

*Chandler  suggests  that  the  discoloration  and  destruction  of 
amalgam  fillings  may  be  due  to  galvanic  action,  the  ingredients  of 
fillings  forming  minute  batteries,  as  it  were,  and  destroying  one 
another. 


INORGANIC   CHEMISTRY. 


151 


ine  70.8.  Molecular  weight,  270.8.  Percentage 
of  mercury,  73.85. 

Preparation  (pharmaceutical):  made  by  tak- 
ing 20  parts  of  mercuric  sulphate  and  16  of 
sodium  chloride,  reducing  each  to  fine  powder, 
mixing  well,  adding  i  part  of  black  oxide  of 
manganese  in  fine  powder,  triturating  thor- 
oughly in  a  mortar,  and  subliming: 

HgSO.   +   2NaCl    =    HgCla  +  Na^SO,. 

Mercuric  Sodium  Mercuric  Sodium 

sulphate.  chloride.  chloride.  sulphate. 

The  manganese  oxide  is  added  to  oxidize 
any  mercurous  salt  which  may  be  present  in 
the  mercuric  sulphate. 

Properties:  corrosive  sublimate  occurs  as  a 
white,  heavy  powder,  or  as  heavy,  colorless, 
rhombic  crystals  or  crystalline  masses.  It  has 
a  metallic,  acrid  taste,  an  acid  reaction,  and  is 
a  violent  poison.  Specific  gravity,  5.4.  It  is 
soluble  in  16  parts  of  cold  water,  and  2  of  boil- 
ing, in  about  2  of  alcohol,  and  4  of  ether.  Its 
ready  solubility  in  alcohol  should  be  noted,  as 
many  compounds  of  the  metals  are  insoluble  in 
alcohol,  or  less  soluble  in  it  than  in  water.  It 
is  a  powerful  germicide,  an  aqueous  solution 
of  I  in  20000  destroying  the  spores  of  bacilli  in 
ten  minutes.  A  solution  of  i  in  5000  is  used  as 
a  disinfectant.  Aqueous  solutions  gradually 
decompose  on  exposure  to  light,  or  in  contact 
with  organic  substances,  such  as  sugar,  gum, 
extracts,  resin,  etc.      When  mercuric  chloride 


152  DENTAL   CHEMISTRY. 

is  being-  powdered,  it  should  be  kept  moist  with 
alcohol  to  prevent  the  poisonous  dust  from 
rising. 

Dental  uses:  mercuric  chloride  in  i  in  20000 
solution — half  a  grain  in  twenty-one  fluid  oun- 
ces of  water  (metric,  0.032  grammes  in  620  C.c.) 
— is  used  as  an  antiseptic.  As  a  germicide,  i 
part  in  2500  of  water;  i  in  5000  as  a  disinfectant. 
It  is  used  as  a  lotion,  injection,  or  gargle. 

Toxicology:  corrosive  sublimate  is  a  power- 
ful, irritant  poison,  and  external  application  of 
it  has  been  often  attended  by  fatal  results.  In 
poisoning  from  internal  administration,  white  of 
egg  in  milk,  or  else  wheat  flour  mixed  with 
milk,  should  be  given;  vomiting  should  be 
encouraged  by  emetics.  White  of  egg  in  milk 
should  be  administered  two  or  three  times 
daily  for  some  weeks.  If  salivation  is  trouble- 
some, gargles  of  chlorate  of  potash  and  of  alum 
should  be  used.  In  chronic  poisoning,  ptyalism 
is  a  prominent  symptom. 

In  chronic  mercurial  poisoning  the  teeth  are 
said  to  become  brittle. 

233.    Mercurous  chloride  or  calomel  :— 

Synonyms:  mild  chloride  of  mercury,  subchloride  of 
mercury,  submuriate  of  mercury,  Hydrargyri  Subchlori- 
dum,  protochloride  of  mercury.  Ofificial  name,  Hydrar- 
gyri Chloridum  Mite. 

Theoretical  constitution:  HgiCU,  two  atoms  of  mercury 
(together  bivalent)  and  two  of  chlorine;  400  parts  by 
weight  of  mercury,and  70.8  by  weight  of  chlorine.      Mole- 


INORGANIC   CHEMISTRY.  153 

cular  weight,  470.8.      Its   formula  is   sometimes   written 
HgCl. 

Preparation:  either  (i)  by  subliming  mercuric  sulphate 
10  parts  with  sodium  chloride  5  parts,  7  parts  of  metallic 
mercury  having  been  previously  triturated  with  the  moist- 
ened mercuric  sulphate. 

HgSOt  +  Hg  =  HgaSO^;  then 
Hg.SO,  +  2NaCl  =   Hg^CU  +  Na^SO,. 
Mercurous  sulphate  and  sodium  chloride  yield  mercurous 
chloride  and  sodium  sulphate.    Or  (2)  by  precipitating  by 
hydrochloric  acid  a  solution  of  300  grams  of  mercury  in 
270  C.c.  of  suitably  diluted  nitric  acid. 

Properties:  sublimed  calomel  is  a  fine,  white  powder 
with  very  slight  tinge  of  yellow.  Tasteless,  insoluble  in 
both  water  and  alcohol.  Sp.  gr.,  6.56.  Completely 
volatilized  by  heat.  Precipitated  calomel  is  bulkier  than 
sublimated  calomel.  Exposed  to  sunlight,  it  acquires  a 
grayish  tinge  becoming  partially  decomposed  into  metal- 
lic mercury  and  corrosive  sublimate;  boiled  with  water, 
the  same  change  takes  place  slowly,  and  a  mixture  of  it 
with  sugar  contains,  after  some  time,  an  appreciable 
amount  of  the  mercuric  chloride.  Mixed  with  water,  it 
should  give  no  white  precipitate  with  ammonia.  Given 
internally  in  sufficient  quantity  it  produces  salivation; 
cases  are  also  on  record  where  external  application  of  it 
has  produced  salivation. 

234.    Mercuric  Sulphide- 
Synonyms:  sulphide  of  mercury,  cinnabar, 

vermilion. 
Theoretical    constitution  :     Hg:S,    mevcuvic 

sulphide.     Molecular  weight,  231.7. 

Preparation:  it  occurs  as  an  ore  and  is  then 

termed  cinnabar.     Made  artificially,  it  is  called 

vermilion. 


154 


DENTAL   CHEMISTRY. 


The  brilliancy  of  vermilion  depends  much 
on  the  manner  in  which  it  is  prepared,  and  on 
the  purity  of  the  substances  used  in  making-  it. 
One  method  of  preparation  is  to  heat  to  I22°F. 
the  following  mixture:  mercury,  300  parts;  sul- 
phur, 114  parts;  potassium  hydrate,  75  parts; 
water,  450  parts.  The  presence  of  potassium 
hydrate  facilitates  the  reaction.  The  mass, 
which  is  at  first  black,  becomes  red  in  the 
course  of  several  hours;  in  order  to  cool  it,  it 
is  poured  into  cold  water,  collected  on  a  filter, 
washed,  and  dried.  Several  kinds  of  vermilion 
are  found  in  commerce;  the  Chinese  (made  in 
the  dry  way  by  subliming  a  mixture  of  sulphur 
I  part  and  mercury  7  parts  in  small  lots)  the 
German,  and  the  French.      Vermilion  should 

sublime  without  residue,  if  pure.* 
235.    Mercuric  Iodide.— 

Synonyms:  biniodideof  mercury,  red  iodide  of  mercury, 
deut-iodide  of  mercury.  Official  name,  Hydrarg5''ri 
lodidum  Rubrum. 

Theoretical  constitution:  Hgl2,  mercuric  iodide.  Mole- 
cular weight,  453.2. 

Preparation:  formed  when  solution  of  potassium  iodide 
is  cautiously  added  to  solution  of  mercuric  chloride, 
HgCl.      +       (KI)3       =       Hgl^      +       2Ka. 

Mercuric  Potassium  Mercuric  Potassium 

chloride.  iodide.  iodide.  chloride. 

Properties:  occurs  as  a  fine,  heavy,  crystalline,  scarlet- 
red  powder.  Nearly  insoluble  in  water,  but  soluble  in  hot 
alcohol,  in  solution  of  potassium  iodide  and  of  sodium 
chloride.     Is  a  powerful  irritant  poison. 

♦Shown  by  heating  dry  in  a  tube  called  a  reduction  tube. 


INORGANIC   CHEMISTRY.  155 

236.  Mercuroiis  Iodide. — 

Synonyms:  protiodide  of  mercury,  yellow  iodide,  green 
iodide. 

Theoretical  constitution:  Hg^Oz  or  Hgl  (like  HgCl). 

Preparation:  made  by  triturating  together  with  a  little 
alcohol  127  parts  of  iodine  and  200  of  mercury. 
Hg,        4-         I3        =         HgJ, 

The  trituration  is  continued  until  there  is  obtained  a 
green  mass,  which,  after  washing  in  boiling  alcohol,  is 
dried. 

Properties:  mercurous  iodide  is  a  green-yellow  powder, 
insoluble  in  water,  alcohol,  and  ether.  Exposed  to  the 
action  of  light,  heat,  alkaline  chlorides  or  iodides,  it  is 
transformed  into  mercury  and  mercuric  iodide. 

237.  Tellurium.— 

Symbol'.  Te.  Latin  name:  Tellurium.  Equivalence'. 
II,  IV,  VI.  Specific  Gravity:  6.18 — 6.24.  Atomic  weight: 
128.  Revised  atomic  tv eight:  127.960.  Electrical  state:  — 
Fusing  point:  little  below  red  heat.  Malleability,  ductility: 
brittle.  Conducting  pozver  (heat):  bad  conductor.  Con- 
ducting poivcr  (electricity):  bad  conductor.  Solubility: 
soluble  in  hot  sulphuric  acid,  in  hot  caustic  alkali  solu- 
tions; attacked  by  hot  nitric  acid.  Direct  combinatio7is : 
hydrogen,  oxygen,  sulphur,  bromine,  chlorine,  iodine. 
Color  and  appearance:  silver  white.  Structure  :  crystallizes 
in  rhombohedrons;  like  As  and  Sb.  Consistence :  hard  and 
brittle.      Compounds  :  tellurides;  telluric,  tellurous. 

Properties  and  preparation:  tellurium  is  in  physical 
properties  a  metal,  though  chemically  allied  closely  to 
sulphur  and  selenium.  It  is  found  native,  though,  in 
Hungary,  and  in  combination  with  bismuth,  lead,  gold 
and  silver.  It  melts  at  500°  C.  When  heated  in  the  air 
it  takes  fire  and  burns  with  a  blue  flame  tinged  with 
green. 


J56  DENTAL   CHEMISTRY. 

238    Sulphur.— 

Symbol'.  S.  Atojiis  in  molecule'.  S2  and  Sg.  Atomic  weight. 
32,  Molecular  weight.  64.  Density,  of  vapor,32.  Specific 
gravity.  2.04.  Weight  of  one  litre  of  vapor'.  2.86  grammes  at 
1000°  C.  How  liquefied',  melts  at  II4°C  (237°  F.)  Solubility. 
insoluble  in  water.  Best  solvent:  carbon  disulphide. 
Nearly  insoluble  in  alcohol. 

Occurrence  in  nature:  occurs  free  in  earth  of  volcanic 
regions  of  Sicily, , 

How  made:  distill  crude  brimstone  in  retort;  vapor 
conducted  into  large  chamber  condenses  in  form  of  pow- 
der known  ^s,  flowers  of  sulphur.  Sulphur  lotum  is  flowers 
of  sulphur  which  has  been  washed.  Sulphur  may  be  made 
by  precipitation  from  sulphides  by  acids. 

Properties:  affinity  for  many  of  the  metals,  for  oxygen, 
carbon,  etc.  Forms  many  compounds.  Lemon  yellow 
solid,  melting  at  234°  F.,  and  boiling  at  824''  F.  Brittle, 
tasteless,  odorless.  Does  not  conduct  electricity  or  heat. 
Precipitated  sulphur  is  almost  white  in  color. 

Use  in  dentistry:  flowers  of  sulphur  is  used 
in  the  manufacture  of  dental  rubbers,  as  a 
vulcanizingf  material.  Caoutchouc  is  heated 
till  soft,  then  ground  with  15  or  20  per  cent,  of 
sulphur  and  subjected  to  heat,  pressure,  and 
moisture. 

Sulphurous  acid:  this  substance,  H2SO3,  is  made  by 
dissolving  sulphurous  anhydride,  SOj,  in  water.  [Sul- 
phurous anhydride  is  made  by  burning  sulphur  and  col- 
lecting the  fumes].  Sulphurous  acid  is  an  unstable  liquid 
of  suffocating  odor.  Its  compounds  are  sulphites.  It  is 
used  for  bleaching  purposes,  and  should  always  be  freshly 
prepared, 

239,  Hydrogen  Sulphide  or  Sulphuretted 
Hydrogen.— 


INORGANIC    CHEMISTRY.  157 

Synonyms:  hydric  sulphide,  sulphydric  acid, 
hydrosulphuric  acid,  Acidum  Hydrosulphuri- 
cum. 

Theoretical  constitution:  HaS,  two  atoms  of 
hydrogen  to  one  of  sulphur;  by  weight,  i6 
parts  of  sulphur  to  i  of  hydrogen;  molecular 
weight,  34 ;  density,  17.2  *  sp.  gr.,  1.192. 
Weight  of  a  litre,  i.540- 

Origin  and  manufacture:  it  is  found  in  vol- 
canic gases,  in  some  mineral  springs,  and  as  a 
result  of  the  decomposition  of  organic  matter 
containing  sulphur,  as  in  the  intestines  and 
in  teeth.  It  is  usually  made  by  the  action  of  a 
dilute  acid  on  a  sulphide,  as  for  example: 
FeS    +     H,SO,    =     FeS04  +     H^S 

Ferrous  sulphide.  Sulphuric  acid.  Ferrous  sulphate.    Hydrogen  sulphide 

Properties:  colorless,  fetid  gas,  combustible, 
soluble  in  water,  readily  recognized  by  its  odor, 
(that  of  rotten  eggs)  valuable  as  a  re-agent, 
yields  precipitates  with  salts  of  many  metals. 
Blackens  unsized  paper  saturated  with  solution 
of  sugar  of  lead.     Poisonous. 

Application  to  dentistry:  its  odor,  if  recog- 
nized in  the  breath,  indicates  that  decomposi- 
tion is  going  on  somewhere  in  the  mouth. 

Its  action  on  the  various  metals  and  com- 
pounds used  in  dentistry  is  of  the  utmost  im- 
portance. It  forms  sulphides  with  silver, 
mercury,  lead,  copper,  bismuth;  these  sulphides 
are  all  dark  in  color,  and  the  blackening  ob- 


158  DENTAL    CHEMISTRY. 

served  in  amalgam  filling's  is  due  to  formation 
of  them.  It  also  forms  sulphides  with  arsenic, 
antimony,  cadmium,  and  tin,  but  these  sulphides 
are  not  black;  the  sulphide  of  arsenic  is  yellow, 
that  of  antimony  orange,  cadmium  yellow,  tin 
yellow  or  brown.  Sulphuretted  hydrogen  does 
not  act  on  metallic  gold,  platinum,  palladium, 
iridium,  nor  does  it  blacken  iron,  cobalt,  nickel, 
manganese,  zinc,  chromium,  or  aluminium. 

240.    Hydrogen  Sulphate  or  Sulphuric  Acid. — 

Synonyms:  hydric  sulphate,  oil  of  vitriol,  dihydric  sul- 
phate, vitriol,  spirit  or  essence  of  vitriol. 

Theoretical  constitution:  H2SO4,  hydrogen  sulphate,  an 
oxacid  composed  of  two  atoms  of  hydrogen,  one  of  sul- 
phur, and  four  of  oxygen;  by  weight  two  parts  hydrogen, 
32  of  sulphur,  64  of  oxygen.  Molecular  weight,  98.  Its 
salts  are  sulphates',  for  example,  zinc  ^nd  sulphuric  acid 
form  zinc  sulphate. 

Preparation:  the  crude  acid  is  prepared  by  the  action  of 
nitric  acid  on  sulphurous  oxide  producing  sulphuric  oxide, 
which  uniting  with  water  forms  sulphuric  acid.  The  sul- 
phurous oxide  may  be  made  by  burning  sulphur  in  air 
The  acid  is  concentrated  by  evaporation  until  a  sp.  gr  of 
1.84  is  obtained,  when  it  contains  about  96  per  cent,  of 
pure  sulphuric  acid. 

Properties :  colorless,  odorless,  heavy,  oily  liquid. 
Generates  heat  on  addition  of  water  Very  caustic. 
Stains  fabrics  reddish,  and  chars  organic  matter.  Stain 
removed  by  ammonia.  Valuable  for  drying  gases  on 
account  of  its  affinity  for  moisture.  Sp.  gr.  (pure)  1.848; 
official,  1.843. 

The  charring  of  organic  matter  by  sulphuric  acid  is  due 
to  the  fact  that  it  unites  with  the  hydrogen  and  oxygen 


INORGANIC   CHEMISTRY.  259 

in  them,  leaving  behind  compounds  so  carbonaceous  that 
the  black  color  predominates.  It  corrodes  animal  tissues. 
Starch  or  cellulose  boiled  with  dilute  sulphuric  acid  is 
converted  into  glucose,  cane  sugar  into  levulose  and 
glucose.  Sulphuric  acid  dissolves  most  of  the  metals,  but 
has  little  action  on  lead. 

Aaduni  sulphuncum,  U.  S.  P.,  called  the  C.  P.  acid,  sp.gr. 
1.84.     Contains  at  least  96  per  cent,  of  H2SO4. 

Aciduni  sulphiiricum  dilutum,  U.  S.  P.,  sp.  gr.,  1.067;  i  part 
of  sulphuric  acid  by  weight  to  9  parts  of  distilled  water. 

Acidiim  sidphuricum  aroinaticuin,  about  same  strength  as 
dilutiini;  contains  alcohol,  cinnamon  oil,  and  tincture  of 
ginger. 

Application  to  dentistry:  in  the  dental  labor- 
atory the  acid  is  used  for  cleaning"  metallic 
plates  previous  to  soldering  and  after  soldering. 
Its  action  is  more  vigorous  when  it  is  diluted 
with  water,  say  with  about  one-third  of  water, 
heat  being  generated.  Its  action  on  hemp 
paper  is  to  reduce  it  to  pyroxylin,  hence  it  is 
used  in  the  preparation  of  celluloid  base. 

In  dental  therapeutics,  in  dilute  form,  it  is 
used  as  a  local  application  in  various  affections 
of  the  mouth.  It  is  caustic,  and  will  dissolve 
thin,  carious  portions  of  bone. 

Toxicology:  the  concentrated  acid  (or  the  dilute  in 
large  doses)  is  a  corrosive  poison.  Its  stain  on  cloth  is 
usually  a  dirty  brown  or  reddish  brown,  and  the  cloth  be- 
comes rotten  and  damp.  It  chars  wood.  Vomited  mat- 
ters will  contain  a  brownish-colored,  bloody  liquid  with 
free  acid.  The  treatment  is  to  give  lime,  magnesia, 
sodium  carbonate,  preferably  in  milk.  The  stomach  pump 
should  not  be  used  in  cases  of  poisoning  from  acids.   Burns 


160  DENTAL   CHEMISTRY 

from  the  acid  should  be  treated  like  those  of  hydrochloric 
acid. 

241.    Oxygen.— 

Symbol:  O.  Atoms  in  molecule:  O2.  Atom- 
ic weight:  16.  Molecular  weight:  32.  Den- 
sity: 16.  Specific  gravity:  1. 10563,  (air=i). 
Weight  of  one  litre  of  gas:  1.43  grammes. 
How  liquefied:  pressure  of  300  atmospheres 
and  temperature  of  — 140°  C.  Solubility: 
water  dissolves  3  per  cent,  of  its  volume  of 
oxygen  gas. 

Occurrence  in  nature:  constitutes  20.93  P^r 
cent,  by  volume  of  atmospheric  air.  Combined 
with  other  elements  constitutes  two-thirds  of 
the  entire  globe,  eight-ninths  of  all  water,  one- 
half  the  weight  of  minerals,  three-quarters  of 
the  weight  of  animals,  and  four-fifths  of 
vegetables. 

How  made:  by  heating  KCIO3  and  MnOa: 
2KCIO3      =      2KCI      +      3O2. 

Potassium  Potassium  Oxygen, 

chlorate.  chloride. 

Properties:  has  affinity  for  all  elements  save 
fluorine.  Is  a  gas,  colorless,  odorless,  tasteless, 
transparent.  Supports  combustion  and  hence 
life.  Oxidation  is  the  term  for  the  combina- 
tion of  substances  with  oxygen.  Oxidizing 
agents  are  those  which  part  easily  with  their 
oxygen  as  HNO3,  KNO3,  KCIO3. 

Use  in  dentistry:  a  body  is  called  "combus- 
tible "  when  it  unites  readily  with  oxygen,  heat 


INORGANIC   CHEMISTRY.  161 

and  light  being  at  the  same  time  Hberated.  It 
is  the  oxygen  in  the  air  which  supports  com- 
bustion, and  which  affords  us  our  artificial  heat 
and  light.  Substances  which  burn  with  diffi- 
culty in  the  air,  owing  to  the  latter  not  being 
pure  oxygen  but  a  mixture  of  oxygen  with 
nitrogen,  will  burn  in  pure  oxygen  with  great 
readiness.  Oxygen  blowpipes  are  those  in 
which  the  flame  is  blown  with  a  jet  of  oxygen; 
oxyhydrogen  blowpipes,  those  where  the  hy- 
drogen burns  in  a  stream  of  oxygen  gas,  pro- 
ducing a  heat  which  fuses  refractory  substances 
such  as  flint,  quartz,  etc.,  and  melts  the  various 
metals.  Some  metals,  as  platinum,  which  can 
not  be  fused  in  a  furnace  maybe  melted  by  the 
oxyhydrogen  flame. 

The  Atmosphere. — Under  the  head  of  oxygen 
and  nitrogen,  air  must  be  considered,  which  is  not  a  com- 
pound, but  when  pure  is  a  viixture  of  20.93  parts  of  oxygen 
by  volume  to  79.07  of  nitrogen.  By  weight,  23  parts  of 
oxygen  to  'j'j  of  nitrogen.  In  the  air  which  we  breathe 
are  found  small  quantities  of  other  substances  such  as 
watery  vapor,  carbon  dioxide,  ozone,  ammonia,  nitric  and 
nitrous  acids,  hydrocarbons,  solid  particles  of  dust,  sodium 
chloride,  vegetable  -germs  or  spores,  bacteria,  etc.,  etc. 
Air  in  which  animals  are  confined  contains  some  of  the 
organic  exhalations  from  their  bodies;  in  the  neighbor- 
hood of  large  cities  the  air  is  contaminated  by  various 
substances  like  sulphuretted  hydrogen  poured  forth  from 
manufacturing  establishments,  furnaces,  etc.,  etc.  The 
air  of  cities  contains  more  bacteria  than  that  of  the 
country.     A  cubic  metre  of  Paris  air  was  found  to  contain 


1Q2  DENTAL    CHEMISTRY, 

3910  bacteria,  as  compared  with  455  in  a  cubic  metre  of 
country  air.  Hospital  air  has  been  found  to  contain 
40,000  to  79,000  microbes  to  the  cubic  metre. 

TRIADS. 

242.  The  following  is  a  list  of  the  most  important 
triads: 

TABLE  18.      IMPORTANT  TRIADS. 

Bismuth  )        Triads  positive  to 

Gold  j     hydrogen. 

Antimony      ^ 

Arsenicum  I  Triads  negative  to 

Arsenicum  ^  hydrogen, 

rnospnorus  |  ^       ^ 

Nitrogen.  J 

243.    Bismuth. — 

Symbol:  Bi.  Lati7i  name:  Bismuthum.  Equivalence : 
III  and  V.  Specific  gravity :  9.78 — 9.80.  Atomic  weight: 
207.5.  Revised  atomic  weight:  207.5230.  Electrical  state: 
+.  Fusing  point:  507"  F.  Length  of  bar:  1.0014.  Weight 
of  cubic  ft.  i?i  lbs.:  613.0.  Te7isile  strength:  1.5.  Tenacity, 
vtalle ability,  ductility :  brittle.  Conducting  power  {^heat^ :  11; 
(  I  ith  rank).  Co7iducting power  {electricity) :  12;  ( 12th  rank). 
Resistance  to  air:  tarnishes  in  moist  air.  Solubility :  soluble 
in  nitric  acid;  in  hot  sulphuric  acid;  in  aqua  regia.  Direct 
cojnbinations :  oxygen,  chlorine,  bromine,  iodine,  sulphur. 
Color  a7id  appearance :  white  with  bronze  tint;  highly 
crystalline  appearance.  Structure :  crystallizes  in  rhombo- 
hedrons.  Consistence :  hard,  brittle.  Compounds :  bismuth- 
ous  and  bismuthic.  Alloys:  fusible  metal,  pewter, 
pewterer's  solder. 

Use  in  dentistry:  for  making  readily  fusible  alloys. 

Occurrence:    this    metal    occurs    native,    disseminated 


INORGANIC   CHEMISTRY.  Ig3 

through  rocks  in  veins.  It  is  rather  rare  and  is  found  as- 
sociated with  ores  of  nickel,  cobalt,  silver,  and  copper. 
Saxony  and  Bohemia  are  the  chief  sources,  but  it  is  also 
found  in  Transylvania,  England,  United  States,  Sweden, 
Norway,  and  Peru. 

Preparation:  to  extract  the  metal  the  earthy  matters 
containing  it  are  heated  and  the  melted  bismuth  is  collect- 
ed in  suitable  receivers. 

244.  Use  in  dentistry:  the  value  of  bismuth  in 
alloys  is  due  to  its  low  melting-  point,  and  to 
the  fact  that  it  expands  very  considerably  as  it 
solidifies.  Compressed  bismuth  is  lighter  than 
that  which  has  not  been  so  treated.  It  is  more 
easily  vaporized  than  many  metals  and  boils 
at  moderate  white  heat.  It  tends  to  crystallize 
from  fusion  in  a  remarkable  manner,  in  rhom- 
bohedrons  of  great  size  and  beauty,  often  mis- 
taken for  cubes. 

An  alloy  of  tin,  lead,  and  bismuth,  is  employ- 
ed for  testing  the  finish  of  a  die.  Bismuth  is 
used  in  the  dental  laboratory  for  making  readily 
fusible  alloys  for  dies  and  counter  dies.  It 
lowers  the  fusing  point  and  imparts  hardness 
when  used  in  alloys. 

245.  Compounds  of  bismuth. — 

Bismuth  subnitrate:  official  name,  Bismuthi  Subnitras. 
Formula,  BiONOs.HjO.  Molecular  weight,  303.5.  It  is, 
as  will  be  seen  from  the  formula,  the  nitrate  of  the  oxide 
of  bismuth.  It  is  called  bismu//^y/ nitrate  by  some  authors, 
also  bis'muth  trisnitrate  and  oxynitrate.  Recent  investi- 
gators deem  it  not  a  fixed  and  definite  compound,  but 
rather   a   mixture.      The  chemistry  of  its  preparation  is 


164  DENTAL    CHEMISTRY. 

complicated;  bismuth  is  first  dissolved  in  nitric  acid, 
forming  the  nitrate;  next,  bismuth  subcarbonate  is  made 
from  the  nitrate,  by  the  action  of  sodium  carbonate;  the 
bismuth  subcarbonate  is  next  redissolved  in  nitric  acid,  to 
form  bismuth  nitrate  again;  finally,  the  bismuth  nitrate  is 
converted  into  subnitrate  by  action  of  ammonia  water. 
Good  subnitrate  of  bismuth  is  soft,  bulky,  insoluble  in 
water,  soluble  in  nitric  acid.  It  often  contains  arsenic  as 
impurity.  Treatment  in  poisoning,  as  for  arsenic.  Used 
in  dentistry  internally  and  topically. 

246.  Alloys  of  bismuth. — 

Fusible  alloys  are  of  different  compositions,  but  con- 
tain bismuth.  One  is  bismuth  2  parts,  lead  i  part,  tin  i 
part;  melts  at  200°  F.  Another  is  50  bismuth,  12.5  cad- 
mium, 25  lead,  12.5  tin. 

Wood's  metal,  according  to  Essig,  is  bismuth  7,  lead  6, 
and  cadmium  i.     Fuses  at  180°  F. 

247.  GrOld.— 

Symbol:  Au.  Latin  name:  Aurum.  Equivalence:  I,  III. 
Specific  gravity:  19.26  to  19.34.  Precipitated  gold,  19.49. 
Atomic  weight:  196.2.  Revised  atomic  weight:  196.155. 
Electric  state:  +•  Fusijig  point:  2016°  F.  Length  of  bar. 
1. 001 5;  (8th  rank).  Weight  of  cubic  ft.  in  lbs.:  1208.6. 
Tensile  strength:  9.1.  Tenacity:  12;  (6th  rank).  Malleabil- 
ity: i;  (ist  rank).  Ductility  i;  (ist  rank).  Solubility: 
soluble  in  aqua  regia,  free  nascent  chlorine  or  bromine, 
mercury;  unaffected  by  action  of  single  acids,  alkalies,  or 
sulphuretted  hydrogen.  Direct  combinations:  chlorine,  brom- 
ine, phosphorus,  antimony,  arsenic,  rnercury.  Color  and 
appeqratice:  orange  yellow  by  reflected  light,  very  brilliant, 
green  by  transmitted  light.  Lustre  unaffected  by  high 
temperatures.  Consistence:  soft.  Compounds:  auric  and 
aurous.  Alloys:  coinage,  jewelry,  etc.,  etc.  Structure:  iso- 
metric crystals. 


INORGANIC   CHEMISTRY, 


165 


248.  Occurrence:  gold  occurs  native,  that  is, 
uncombined  with  other  metals.  It  is  found 
almost  everywhere,  but  in  most  regions  in 
exceedingly  small  quantities.  It  occurs  in 
England,  Scotland,  Ireland,  Wales,  Hungary, 
Transylvania,  Sweden,  Spain,  Italy,  Siberia,  in 
the  Ural  Mountains,  Japan,  Ceylon,  Borneo, 
Thibet,  Africa,  Brazil,  Chili,  Peru,  Mexico, 
California,  and  Australia.  The  greatest  quanti- 
ties are  now  found  in  Africa,  California,  and 
Australia.  Gold  is  either  in  form  of  alluvial 
gold,  that  is,  washed  down  by  rivers,  or  gold- 
^imrf^,the  metal  being  disseminated  in  thin 
plates  and  branch-like  fragments,  through 
lumps  of  quartz-rock. 

249.  Preparation:  alluvial  gold  is  extracted 
by  washing  the  alluvial  deposits,  the  separation 
of  earthy  matters  being  readily  effected  owing 
to  the  high  specific  gravity  of  gold  (19.3).  In 
California  and  Australia  a  wooden  trough,  six 
feet  long,  resting  on  rockers  and  called  a  cradle, 
is  used.  At  the  head  of  it  is  a  grating,  on 
which  the  alluvial  matter  is  thrown.  A  stream 
of  water,  entering  the  cradle,  flows  through 
and  escapes  at  the  lower  end,  leaving  the  gold 
in  the  trough,  but  carrying  the  earthy  matters 
along  with  it.  Gold-quartz  must  first  be 
crushed,  either  by  passing  it  through  rollers  or 
by  use  of  stampers.  After  pulverization,  the 
gold  is  dissolved  out  by  mercury.      The  amal- 


166  DENTAL    CHEMISTRY. 

gam  resulting-  is  then  subjected  to  pressure  and 
excess  of  mercury  thus  squeezed  out,  the  re- 
mainder being  separated  by  distiUing,  leaving 
the  gold. 

250.  Refilled  gold  may  be  obtained  in  various 
ways.  Chlorine  gas  has  been  used  as  a  refin- 
ing agent,  when  gold  is  to  be  separated  from 
silver.  Nitric  acid  or  sulphuric  acid  may  be 
used.  Sulphuric  acid  converts  silver  or  copper 
into  sulphates,  but  does  not  attack  gold. 

American  gold  is  liable  to  contain  iridium, 
which  may  be  separated  from  it  by  alloying 
the  gold  with  silver,  melting,  and  either  pour- 
ing off  the  gold  and  silver  alloy  from  the  irid- 
ium or  treating  with  nitric  acid  and  then  with 
aqua  regia. 

25 1 .  Cliemically  pure  gold  is  obtained  from 
refined  gold  in  various  ways:  for  example,  refin- 
ed gold  may  be  dissolved  in  aqua  regia,  excess  of 
acid  driven  off  by  heat,  then  alcohol  and 
potassium  chloride  added  to  precipitate  any 
platinum  present.  The  filtered  solution  is  then 
evaporated  over  the  water  bath,  the  residue 
dissolved  in  distilled  water,  until  each  gallon 
contains  not  more  than  half  an  ounce  of  the 
chloride,  the  solution  allowed  to  settle,  the 
supernatant  liquid  siphoned  off,  and  the  gold 
precipitated  in  the  metallic  state  by  one  of  the 
various  precipitants,  such  as  oxalic  acid  or  sul- 
phurous anhydride. 


INORGANIC    CHEMISTRY.  167 

252.  Agents  used  for  Precipitating  Grold: 

gold  may  be  precipitated  in  the  metallic  state 
by  various  substances. 

Oxalic  acid  precipitates  g;old  from  its  chlor- 
ide solution  in  several  forms,  spongy  or  crystal- 
line.    Gentle  heat  favors  the  process.     The 
equation  is: 
2AUCI3  +   3H2C2O4  =  6HC1  +  6CO2  +  2Au. 

Auric  Oxalic  acid.  Hydrochloric  Carbon  Gold, 

chloride.  acid.  dio.xide. 

Sulffhurous  acid  precipitates  gold  in  scales, 
"  not  sufficiently  coherent  or  sponge-like  for 
use  as  a  filling  material."     (Essig). 

Ferrous  sidpJiate  precipitates  gold  in  form  of 
a  light-brown  powder. 

Phosphorus,  when  introduced  into  a  heated 
solution  of  gold  chloride,  becomes  coated  with 
a  film  of  metallic  gold.* 

Zinc  and  other  base  metals  precipitate  gold 
as  a  brown  powder. 

Metallic  salts,  besides  ferrous  sulphate, 
and  organic  acids  besides  oxalic,  precipitate 
gold;  the  latter  best  from  neutral  solutions. 

253.  Crystal  gold  is  obtained  by  reduction 
on  a  platinum  pole  by  the  electric  current. 
Plates  of  pure  gold  are  suspended  in  a  solution 
of  auric  chloride.  These  are  connected  with  a 
battery,  so  that,  as  the  solution  loses  its  gold 
by  deposition  of  the  metal,  it  is  re-supplied  by 
the  suspended  plates. 

*0ther  non-metals  become  coated  in  the  same  way. 


168  DENTAL   CHEMISTRY. 

254.    Pure  gold  may  be  beaten  out  so  as  to 

present  a  surface  650,000  times  its    orig-inal 
area. 

Dentists'  leaf-gold  is  usually  beaten  from  fine  gold;  a 
very  small  quantity  of  any  other  metal  materially  injures 
its  malleability.  To  prepare  leaf  gold,  the  metal  is  first 
melted  in  a  crucible  with  a  little  borax,  poured  into  a  mold 
to  form  an  ingot  ^  inch  high,  the  ingot  annealed  and 
hammered  with  several  annealings,  until  only  I  inch  high, 
passed  between  rollers  until  reduced  to  a  thin  ribbon,  cut 
into  pieces  an  inch  square;  150  of  these  pieces  are  piled 
up,  alternately,  with  pieces  of  tough  paper  or  vellum  4 
inches  square  rubbed  over  with  a  little  fine  plaster-of- 
Paris.  Twenty  vellums  are  then  placed  above,  and  twenty 
below  the  pile,  which  is  firmly  secured  by  passing  two 
strong  belts  of  parchment  across  it.  The  pile  is  placed 
on  a  heavy  block  of  marble,  and  beaten  with  a  hammer 
weighing  about  16  pounds.  After  a  time  the  middle 
leaves  are  shifted  to  the  outside,  and  the  beating  continu- 
ed, until  the  leaves  are  nearly  the  size  of  the  vellums, 
when  they  are  taken  out  and  cut  into  4  squares  measuring 
an  inch  each  way.  They  are  then  made  into  packets, 
with  £^oid  beaters'  skins  in  alternate  layers,  and  beaten  with 
a  ten-pound  hammer.  When  they  are  4  inches  square 
they  are  cut  into  4  equal  squares,  again  made  into  packets 
with  gold-beaters'  skin,  and  hammered  again  with  a  seven- 
pound  hammer  to  about  33^  inches  square.  They  are 
then  lifted  off  the  skin,  cut  down  to  one  size,  and  packed 
between  leaves  of  books.  There  are  usually  25  leaves  in 
a  book,  each  of  which  is  on  an  average  gg^'ooo  of  an  inch 
thick.  They  are  now  usually  beaten  by  mechanical 
power.  These  leaves  show,  when  held  up  to  the  light,  a 
fine  green  color.  Rendered  non-lustrous  by  heat,  the 
color  is  ruby-red.      Weak  solution  of  potassium  cyanide 


INORGANIC   CHEMISTRY  IgQ 

slowly  dissolves  them.  Fine  gold,  i,  e.,  that  which  is  per- 
fectly free  from  impurities,  is  about  as  soft  as  lead.  Its 
fineness  is  expressed  by  use  of  the  term  carats:  gold  coin 
containing  22  parts  gold  to  2  of  alloy  is  said  to  be  22 
carats  fine;  pure  gold  is  24  carats  fine. 

255.  Cohesive  gold,  used  for  filling-  opera- 
tions, rnay  be  obtained  by  heating-  foil  to  red- 
ness, by  which  the  cohesiveness,  which  is 
g-reatly  diminished  by  compression  of  the  fibres 
in  beating-,  is  restored. 

256.  Corrugated  gold,  according-  to  Essig-, 
is  prepared  by  placing-  the  sheets  of  g:old 
between  leaves  of  a  particular  kind  of  unsized 
paper  and  tightly  packing  them  in  iron  boxes, 
which  are  exposed  to  a  temperature  sufficient- 
ly high  to  carbonize  the  paper.  On  cooling, 
the  gold  is  found  to  be  exceedingly  soft,  non- 
cohesive,  and  to  present  a  peculiarly  corrugated 
condition  of  surface. 

Use  in  dentistry:  gold  is  used  by  dentists  m 
fine  powder,  and  in  foil  for  filling  purposes.  It 
is  an  ingredient  of  some  amalgam  alloys,  of 
alloys  for  bases  for  artificial  dentures,  and  of 
solders.  In  minute  division  it  is  used  as  a 
coloring  matter  for  artificial  teeth. 

Gold  containing  palladium  or  platinum  is 
lighter  in  color;  if  it  contains  copper  it  is  red- 
der in  color.  Lead  or  antimony  makes  gold 
brittle,  even  if  in  minute  proportion.  Silver 
whitens  the  color  of  gold. 


170  INORGANIC   CHEMISTRY. 

Table  19. — Effect  on  Gold  of  Alloying. 

Malleability :  impaired;  seriously  by  As,  Sn,  Sb,  Bi,  Pb. 
Ductility:  diminished.  Hardness:  increased.  Tenacity: 
usually  increased.  Specific  gravity :  varies;  with  Zn,  Sn, 
Bi,  Sb,  Co,  sp.  gr.  greater  than  mean  of  components;  with 
Ag,  Fe,  Pb,  Cu,  Ir,  Ni,  less  than  the  mean.  Fusibility: 
usually  increased. 

Gold  and  Copper  have  great  affinity  for  one  another  and  may  be 
alloyed  in  all  proportions.  Copper  diminishes  the  ductility  of  gold 
when  it  enters  into  the  combination  in  a  proportion  over  lo  to  12  per 
cent.  Pure  copper  must  be  used  for  alloying.  Gold  and  Silver 
readily  mix  but  do  not  appear  to  form  true  combinations.  One- 
twentieth  of  silver  will  modify  color  of  gold.  Yellow  Gold,  Green 
Gold,  and  Pale  Gold  are  alloys  of  gold  and  silver.  Alloys  of  gold, 
copper,  silver  and  palladium  are  brownish-red  in  color,  hard  as  iron, 
and  never  rust.  Nurnberg  Gold  is  an  alloy  of  copper  go  parts,  gold 
2.5,  add  aluminium  7.5;  it  has  the  color  of  gold  and  remains  un- 
changed. 

The  melting  of  metals  constituting  alloys  is  brought  about  by  use 
of  graphite  crucibles,  the  gold  being  melted  first.  After  it  is  entirely 
melted,  it  is  heated  as  strongly  as  the  furnace  permits  and  the  other 
metals  added  in  as  small  pieces  as  practicable.  The  mixture  is 
stirred  with  an  iron  rod  sharpened  on  the  point  and  previously  heated 
to  redness.  When  it  is  desired  to  toughen  gold,  use  as  a  flux  the 
following:  one  part  charcoal  to  one  sal-ammoniac  adding  to  the  gold 
just  before  melting. 

Phosphor-iridiiim,  as  it  is  called,  has  some  remarkable  properties. 
It  is  prepared  by  Holland's  process,  in  which  iridium  ore  is  heated 
in  a  Hessian  crucible  to  a  white  heat,  and,  after  phosphorous,  has 
been  added,  the  heating  is  continued  for  a  few  minutes.  It  has  the 
power  more  than  any  other  metal  of  retaining  lubricants.  It  is 
slightly  magnetic  when  alloyed  with  iron  and  is  not  attacked  by  acids 
or  alkalies.  The  alloy  with  iron  (50  per  cent  or  less),  is  not  affected 
by  the  best  file. 

[For  further  consideration  of  the  subject  of  alloys  the  reader  will 
find  it  useful  to  consult  special  works,  among  these  may  be  men- 
tioned Krupp's  book  which  has  lately  been  translated  into  English 
with  additions  by  Brannt]. 


INORGANIC   CHEMISTRY. 


171 


Table  20. — Specific  Effects  of  Certain 
Metals  on  Gold  when  Alloyed 

WITH  IT. 


Metal. 

Effect. 

Zinc: 

forms  hard,  white,  brittle  alloy  (when  in  equal  propor- 
tions); does  not  unite  so  intimately  as  lead  or  tin. 

Tin: 

renders  gold  intractable  to  remarkable  degree.  The 
combination  is  attended  by  contraction(?). 

Lead  : 

renders  gold  intractable.* 

Antimony: 

renders  gold  intractable.  One  part  in  1920  too  brittle 
for  successful  lamination. 

Bismuth: 

in  almost  inappreciable  quantities  renders  gold  in- 
tractable, as  1  in  1S»20. 

Iron: 

does  not  sensibly  affect  malleability,  in  the  proportion 
of  1  to  11. 

Mercury: 

dissolves  gold,  and  combines  with  it  at  all  tempera- 
tures, but  more  readily  when  gold  is  in  state  of  fine 
division  and  when  heat  is  applied. 

Arsenic: 

malleability  of  gold  affected,  even  by  vapor  of  arsenic. 
The  color  of  the  gold  may  not  be  changed,  even 
when  it  has  become  brittle. 

Silver: 

renders  gold  more  fusible,  increases  hardness,  does 
not  materially  affect  malleability,  makes  color 
lighter. 

Palladium: 

equal  parts:  gray  color,  less  ductile.  4  gold,  1  palla- 
dium: white,  hard,  ductile.  Merest  traces  of  palla- 
dium render  gold  brittle. 

Copper: 

hardens  and  toughens  gold,  gives  deeper  color,  ren- 
ders it  capable  of  receiving  rich  polish,  does  not 
practically  impair  its  malleability. 

Platinum: 

in  small  proportions  hardens,  and  renders  more  elas- 
tic, without  impairing  malleability.  Makes  color 
pale  and  dull,  if  equal  weights.  Excess  of  platinum 
renders  alloy  infusible  in  blast  furnace. 

*A  minute  quantity  of  lead  will  color  gold  brownish,  render  it 
brittle,  and  reduce  its  tenacity  from  resistance  to  18  tons  per  square 
inch  to  only  5  tons. 


172  DENTAL   CHEMISTRY. 

Table  21. — Appearance  of  Gold  Alloys. 


Alloy  metal 

Color,  etc. 

Tin: 

Light  colored,  very  brittle. 

Lead: 

Dull  colored,  brittle. 

Platinum: 

Grayish  or  dull  colored,  malleable,  tough,  elastic. 

Zinc: 

Unequally  malleable,  brittle  in  spots. 

257.  Gold  Alloys  and  Alloys  Resembling  Gold:  gold 
coinage:  gold  90,  copper  10.  Gold  jewelry  and  plate: 
gold  75  to  92,  copper  25  to  8. 

Green  gold:  gold  75,  silver  25. 

Red  gold:  gold  75,  copper  25. 

Dutch  gold  is  merely  a  species  of  brass,  usually  sold  in 
very  thin  leaves  or  sheets,  It  is  formed  of  11  parts  cop- 
per with  2  of  zinc. 

Poors  gold  \s  iron  pyrites,  a  sulphide  of  iron. 

Oreide  is  a  species  of  brass. 

Pinchbeck  gold  is  a  kind  of  brass;  MajDiheim  gold  and 
Similor  are  also  brass. 

Talmi gold '\'s>  90  copper,  to  10  aluminium,  as  is  alumin- 
ium bronze. 

Mosaic  gold  is  a  definite  chemical  compound,  SnSg, 
stannic  sulphide,  made  by  heating  in  a  flask  at  low  red 
heat,  12  parts  tin,  6  mercury,  6  ammonium  chloride,  and  7 
flowers  of  sulphur;  everything  sublimes  except  the  stannic 
sulphide  which  remains  in  the  bottom  of  the  flask.  [The 
name  "  Mosaic  gold  "  is  sometimes  given  to  substances 
other  than  stannic  sulphide]. 

Oold  base  plate:  different  formulas  are  in 
vogue,  but  the  constituents  are  in  the  main 
gold,  copper,  and  silver;  some  contain  platinum 
as  well.      18  carat  gold  plate  is  made  by  two 


INORGANIC   CHEMISTRY.  173 

formulas:  No.  i  contains  i8  dwts.  pure  gold,  4 
fine  copper,  2  fine  silver;  No.  2  is  20  dwts.  gold 
coin,  2  fine  copper,  2  fine  silver.  Gold  plate, 
22  carats  fine,  is  22  dwts.  pure  gold,  i  dwt.  fine 
copper,  18  grains  silver,  6  grains  platinum. 

Grold  plate  for  clasps,  wires,  etc.,  etc.:  gold 
used  for  this  purpose  should  contain  sufficient 
platinum  to  render  it  firmer  and  more  elastic. 
A  20  carat  alloy  for  such  purposes  is  made  by 
2  formulas:  No.  i  is  20  dwts  pure  gold,  2  fine 
copper,  I  fine  silver,  i  platinum;  No.  2  is  20 
grains  coin  gold,  8  grains  fine  copper,  10  grains 
fine  silver,  20  grains  platinum. 

Gold  solder  is  22.2  copper,  66.6  gold,  ii.i 
silver. 

258.    Compounds  of  Gold. — 

Auric  Chloride  or  the  terchloride  of  gold,  AuClg.  Pre- 
pared by  dissolving  gold  in  aqua  regia,  using  gentle  heat. 
The  solution  evaporated  to  dryness,  over  the  water  bath, 
yields  ruby-red,  prismatic  crystals,  deliquescent,  soluble  in 
water,  alcohol,  ether,  and  of  disagreeable,  styptic  taste; 
auric  chloride  stains  the  skin  purple,  but  the  stain  is 
readily  removed  by  potassium  cyanide.  It  is  an  escharo- 
tic  and  disinfectant,  and  dissolved  in  ether  is  used  in 
dentistry  as  an  obtunding  agent.  Solutions  should  be 
kept  in  glass  stoppered  bottles,  as  the  gold  tends  to 
deposit  from  solutions.     It  is  a  poison. 

Auric  Oxide,  AU2O3,  is  prepared  from  the 
terchloride  by  digesting  magnesia  in  it,  by 
which  magnesium  aurate  is  formed.  The  lat- 
ter is  decomposed  by  nitric  acid  and  the  residue 


174  DENTAL   CHEMISTRY. 

auric  oxide,  when  dried,  is  a  dark  brown,  easily 
decomposing  powder. 

Purple  of  Cassius  is  a  compound  of  gold, 
tin,  and  oxygen. 

It  may  be  prepared  by  treating  gold  chloride 
with  solution  of  stannous  chloride,  or  by  adding 
stannous  chloride  to  a  mixture  of  stannic  chlor- 
ide and  auric  chloride,  as  follows:  7  parts  of 
gold  are  dissolved  in  aqua  regia,  and  mixed 
with  2  parts  of  tin  also  dissolved  in  aqua  regia; 
this  solution  is  largely  diluted  with  water,  and 
a  v/eak  solution  of  i  part  tin  in  hydrochloric 
acid  is  added  drop  by  drop,  till  a  fine  purple 
color  is  produced.  The  purple  of  Cassius  re- 
mains suspended  in  water,  but  subsides  gradu- 
ally, especially  if  some  saline  substance  be 
added.  Purple  of  Cassius  is  a  brown,  reddish 
purple  or  black  powder  soluble  in  ammonia. 
It  is  used  as  a  coloring  for  porcelain.  Its 
composition  is  doubtful,  probably  Au20.Sn02- 
SnOSn02.4H20.,  that  is  a  double  stannate  of 
aurous  oxide  and  stannous  oxide. 

259.    Antimony.— 

Symbol :Sb.  Latin  name:  Stibium.  Equivalence:  III 
and  V.  Specific  gravity :  6.72.  Atomic  weight:  120.  Re- 
vised atomic  weight :  119.955.  Electrical  state :  — .  Fusing 
point:  842°  F.  Length  of  bar:  i.ooii;  (nth  in  rank). 
Weight  of  cubic  feet  in  lbs:  419.5.  Tensile  stroigth:  0.5. 
Tenacity,  malleability,  ductility :  brittle.  Conducting  power 
{heat):  10;  (lOthrank).  Conducting  power  {elcctncity) :  46; 
(silver  =  1000);  (nth  rank).     Resistance  to  air,  etc :  takes 


INORGANIC    CHEMISTRY.  275 

fire  at  red  heat,  but  scarcely  tarnishes  in  air.  Solubility : 
in  boiling  hydrochloric  acid  to  which  a  little  nitric  has 
been  added:  in  fine  powder,  dissolved  by  solutions  of 
higher  sulphides  of  Na  and  K.  Direct  combinations :  with 
chlorine,  sulphur,  oxygen,  bromine,  iodine.  Color  and  ap- 
pearance: brilliant  bluish-white,  like  zinc.  Structure: 
rhombohedral  crystals  like  arsenic  and  red  phosphorus; 
there  is  also  an  amorphous  form.  Consistence:  hard,  brittle. 
Compounds:  antimonous  (III)  and  antimonic  (V).  Alloys: 
Britannia  metal,  pewter,  type  metal,  Babbitt's  anti-friction 
metal. 

Occurrence:  antimony  is  found  both  native  and  com- 
bined. It  occurs  free  in  Germany.  Gray  antimony  ore, 
the  sidphide,  Sb-iSs,  occurs  in  England,  France,  Hungary, 
and  Borneo.  An  oxide  is  found  in  Algeria.  Redantitnony, 
which  is  a  compound  of  the  oxide  and  sulphide  is  found 
in  Tuscany. 

Antimony  is  also  found  in  the  United  States  and  in 
Mexico. 

Preparation:  the  principal  ore  (stibnite),  which  is  a  sul- 
phide, yields  regulus  of  antimony  (metallic  antimony) 
when  melted  with  metallic  iron.  A  purer  article  is  ob- 
tained by  roasting  the  crushed  ore,  converting  it  into  an 
oxide;  the  latter  is  then  fused  with  charcoal. 

Properties:  the  metal  is  not  attacked  by  hydrochloric 
acid.  Nitric  acid  converts  it  into  a  white,  insoluble  oxide. 
Aqua  regia  dissolves  it,  forming  a  chloride  called  "  but- 
ter of  antimony";  water  converts  this  chloride  into  an 
oxychloride. 

SbCU       +       H2O       =       SbOCl       -f        2HCI. 

Autimonous  Water.  Antimony  Hydrochloric 

chloride.  oxychloride.  acid. 

This  equation  illustrates  the  formation  of  an  oxychlor- 
ide. 

260.  Uses  in  dentistry  and  the  arts:  antimony  is  valu- 
able as  a  constituent  of  alloys:  to  give  hardness  to  other 


176  DENTAL   CHEMISTRY. 

metals,  and  to  cause  them  to  expand  and  completely  fill 
moulds  on  cooling. 

It  can  be  distinguished  from  other  metals  by  its  brittle- 
ness,  crystalline  structure,  and  hardness;  it  can  easily  be 
pulverized,  and  breaks  from  a  slight  tap  of  a  hammer.  It 
is  not  deemed  a  metal  by  some,  being  classed  with  arsenic 
and  phosphorus,  rather  than  with  the  metals.  It  burns 
at  red  heat,  with  odor  of  garlic  and  with  white  fumes, 
suggesting  arsenic.  The  amalgam  with  mercury  is  soft 
and  decomposed  by  contact  with  air  or  water,  antimony 
separating.     It  has  been  used  in  dental  amalgam  alloys. 

261.  Boron.— 

Symbol:  B.  Latin  name:  Boron.  Equivalence:  III. 
Specific  gravity :  2.63.  Atojnic  wt,  {approx.) :  10.9.  Atojnic 
wt.  {revised):  10.941.  Electrical  state:  — .  Properties: 
amorphous,  greenish  powder,  soluble  in  melted  aluminium. 
Boron  is  not  used  in  dentistry. 

262.  Hydrogen  Orthoborate  or  Boracic  Acid. — 

Synonyms:  boric  acid,  orthoboric  acid,  sedative  salt  of 
Romberg.     Ofificial  name,  Acidum  Boricum. 

Theoretical  constitution:  orthoboric  acid,  H3BO3, 
graphically,  B"'  (H0)3.  Composed  of  three  atoms  of 
hydrogen,  one  of  boron,  and  three  of  oxygen.  By  weight, 
3  parts  of  hydrogen,  11  of  boron,  and  48  of  oxygen. 
Molecular  weight,  62. 

Preparation:  boracic  acid  is  made  from  borax  by  add- 
ing hydrochloric  acid   to  a  hot  solution  of  the  former, 
which  causes  a  precipitate  of  boracic  acid: 
Na^B.O;    +     2HCI     +     sHoO     =    4H3BO3  +    2NaCl. 

Borax.  Hydrochloric  Water.  Boric  acid.  Common 

acid.  salt. 

Properties:  brilliant,  white,  shining,  odorless,  six-sided 
plates,  greasy  to  the  touch,  slightly  soluble  in  cold  water 
I  part  in  25,  soluble  in  3  parts  hot  water,  soluble  in  6  parts 
alcohol,  soluble  in  glycerine.  Specific  gravity,  1.517  at 
ordinary  temperatures.      Is  a  powerful  antiseptic.     Satu- 


INORGANIC   CHEMISTRY.  ]^77 

rated  with  alcohol,  burns  with  a  green  flame.  Its  solu- 
tions are  but  faintly  acid;  turmeric  paper  moistened  with 
a  solution  of  this  acid  becomes  reddish-brown  on  drying. 
Heated  with  glycerine  forms  boroglycende.  ,  (See  Boro- 
glyceride  under  head  of  Glycerine). 

Use  in  dentistry:  boracic  acid  is  used  for 
various  antiseptic  purposes.  Combined  with 
sodium  sulphite  it  has  been  used  as  a  bleaching- 
agent  for  discolored  teeth.  (See  Boroglycer- 
ide). 

263.    Arsenic- 
Metallic  arsenic  is  not  used  in  medicine  or  dentistry. 
One  of  its  compounds,  arsenous  oxide  ox  anhydride,  is  of  im- 
portance, and  the  term  arsenic  is  usually  applied  to  this 
substance. 

Arsenous  Anhydride. — 

Synonyms:  arsenious  acid,  arsenious  anhy- 
dride, white  arsenic,  ratsbane,  white  oxide  of 
arsenic,  Arseniosum  Oxidum.  Official  name, 
Acidum  Arsenosum. 

Theoretical  constitution:  AsaOg,  arsenous 
oxide,  two  atoms  of  arseni(^o  three  of  oxygen, 
by  weight  150  of  arsenic  to  48  of  oxygen. 
Molecular  weight,  198.  Composed  of  75.76  per 
cent.  As  and  24.24  per  cent.  O.  [The  molecule 
of  vitreous  arsenic  is  thought  to  be  represented 
by  the  formula  AsiOe]. 

Preparation:  arsenous  oxide  occurs  in  nature 
as  arsenic  "  bloom,"  a  term  derived  from  the 
Saxon  bloma,  a  lump.  It  is  obtained  by  roast- 
ing ores  of  other  metals  containing  it  in  a  cur- 


178  DENTAL   CHEMISTRY 

rent  of  air.  The  arsenous  oxide  in  the  roast- 
ing- process  volatiHzes  and  is  condensed  in 
suitable  receiving  chambers  as  a  white  powder. 

Properties:  it  is  found  in  the  form  of  a  fine, 
white,  heavy  powder  or  in  glassy  looking^ 
lumps.  The  powder  is  somewhat  g"ritty,  odor- 
less, tasteless,  permanent  in  air.  Condensed 
from  sublimation  at  752°  F.,  it  is  a  transparent, 
vitreous  mass,  sp.  gr.,  3.738.  When  condensed 
at  temperature  slightly  less,  crystallizes  in 
right  rhombic  prisms.  Vitreous  arsenic,  on 
keeping,  g"radually  becomes  opaque  and 
crystalline.  When  condensed  at  392°  ¥.,  it 
occurs  in  octahedral  crystals,  sp.  gr.,  3.69.  This 
form  is  also  obtained  on  evaporating  a  satu- 
rated aqueous  solution.  Vitreous  arsenic  is 
slightly  more  soluble  than  the  opaque;  100 
parts  boiling  water  dissolve  12  parts  of  the 
vitreous;  on  cooling,  about  three  parts  are 
left  in  solution.  Arsenic  is  soluble  in  hot  HCl, 
in  solutions  of  alkalies  and  of  tartaric  acid. 
Dissolved  in  acids  it  forms  a  binary  compound 
of  arsenic,  as,  for  example,  arsenous  chlo%"ide 
when  dissolved  in  hydrochloric  acid.  Dissolv- 
ed in  alkalies  it  acts  as  the  negative  element 
forming  arsenites  of  the  alkali  metals,  as 
K2HASO3,  potassium  hydro-arsenite. 

Locally,  it  acts  as  an  escharotic,  first  des- 
troying the  vitality  of  organic  structure,  de- 
composition then  ensuing. 


INORGANIC    CHEMISTRY.  179 

It  is  a  powerful  antiseptic,  retarding  putre- 
faction to  a  marked  degree. 

Uses  in  dentistry:  arsenous  oxide  is  used  to 
destroy  the  vitality  of  tooth  pulps;  it  has  also 
been  used  as  an  obtunding  agent.  It  kills  a 
tooth  by  causing  irritation;  there  is  increased 
flow  of  blood  to  the  parts,  the  arteries  are  en- 
larged so  that  there  is  no  return  of  blood 
through  the  veins,  hence  strangulation  at  apex 
of  the  tooth. 

Toxicology:  arsenic  in  doses  of  from  one  to 
two  grains  is  a  powerful  poison.  It  is  poison- 
ous also  even  when  locally  applied.  There  is 
danger  of  absorption  when  arsenic  is  applied 
to  the  teeth. 

The  treatment  of  poisoning  by  this  agent, 
when  administered  internally,  is  to  provoke  or 
promote  vomiting  by  giving  large  quantities  of 
hot  milk  and  water  or  emetics,  as  sulphate  of 
zinc  (5  grains  repeated  in  15  minutes)  or  must- 
ard (teaspoonful  or  two  of  ground  mustard  in 
water);  subcutaneous  injection  of  apomorphine 
hydrochlorate  in  doses  of  15  to  10  of  a  grain  will 
speedily  bring  about  emesis.  The  antidote  to 
arsenic  is  ferric  hydrate,  conveniently  made  by 
adding  Aqua  Ammoniae  to  Tincture  of  Ferric 
Chloride.  A  brownish  substance  is  formed 
ivhich,  separated  from  the  liquid,  may  be  given 
ad  lib.  The  antidote  should  be  given  after 
vomiting  has  been  brought  about.      Finally 


180  DENTAL   CHEMISTRY. 

bland  liquids,  such  as  milk  and  eggs,  should  be 
given;  sugar  and  magnesia  in  milk  are  highly 
recommended.  When  arsenic  has  been  ab- 
sorbed from  local  application  it  is  of  course 
useless  to  give  emetics,  etc.,  the  only  treatment 
possible  being  that  of  treating  the  symptoms  as 
they  appear,  promoting  elimination  by  diur- 
etics as  potassium  nitrate,  etc.,  etc. 

Note:  in  making  the  antidote  for  arsenic  let 
the  precipitate  drain  on  a  wetted  muslin 
strainer  until  most  of  the  liquid  has  run  off, 
gather  up  the  cloth,  press  it  with  the  hands 
until  no  more  liquid  can  be  squeezed  out,  then 
add  water  and  administer.  The  official  hydrate 
is  made  from  solution  of  normal  ferric  sul- 
phate. 

264.    Phosphorus. — 

Symbol:  P.  Atoms  in  molecule:  P^.  Atomic  weight:  31. 
Molecular  weight:  124.  Density,  of  vapor:  62.  Specific 
gravity:  yellow  1.83,  red  2.14.  How  liquefied:  the  yellow 
melts  at  111°  F.  under  water.  Solubility:  yellow  is  insolu- 
ble in  both  water  and  alcohol,  but  soluble  in  carbon 
disulphide,  while  the  red  is  insoluble  in  the  latter. 

Occurrence  in  nature :  does  not  occur  native,  but  as 
phosphates,  etc. 

How  made:  from  ash  of  burnt  bones  by  treating  with 
sulphuric  acid,  and  heating  with  charcoal. 

Properties:  yellow  is  translucent,  waxy,  shines  in  the 
dark,  readily  oxidized,  taking  fire  at  140°  F.  and  must  be 
kept  under  water.  Becomes  covered  with  red  or  white 
coat  on  exposure  to  light;  poisonous.  Red  does  not  in- 
flame readily,  and  is  not  poisonous.      Phosphorus  com- 


INORGANIC   CHEMISTRY.  181 

bines  with  most  elements  except  C,  N,  and    H,  and  redu- 
ces some  metallic  salts  as  of  Cu,  Ag. 

Use  in  dentistry:  phosphorus  is  of  value  as  a  deoxi- 
dizer  in  fusing  refractory  metals  such  as  iridium,  nickel, 
etc. 

Toxicology.  Carious  teeth,  swollen  and  in- 
flamed gums,  finally  necrosis  of  the  jaws, 
usually  of  the  lower  one,  are  often  noticed  in 
those  who  work  in  match  factories.  Most 
cases  of  phosphor-necrosis  originate  in  un- 
sound teeth  or  where  the  gums  are  kept  away 
from  the  teeth  by  tartar. 

About  Tuth  grain  of  phosphorus  is  contained 
in  a  match  head.  In  the  dipping  and  packing 
room  the  matches  are  handled  the  most,  and 
in  damp  weather  the  fumes  are  given  off  so 
that  no  workman  with  carious  teeth  should 
work  in  these  rooms.  Alkaline  mouth-washes 
should  be  used,  and  workmen  should  keep 
their  hands  clean  and  not  eat  in  the  work 
rooms.    Good  ventilation  should  be  secured. 

The  use  of  red  phosphorus  instead  of  yel- 
low is  to  be  advised,  as  the  former  is  not 
poisonous. 

265.  Anhydrous  Phosphoric  Acid,  so  called,  is  phos- 
phoric anhydride,  i.  e.,  phosphoric  oxide  or  phosphorus 
pentoxide,  P2O5,  and  is  formed  by  the  rapid  burning  of 
phosphorus  in  air  or  in  oxygen.  It  is  very  deliquescent. 
It  forms  with  water  a  solution  of  the  glacial  acid,  HPO3. 
P,05  +  H2O  =  H.P^Oe  =  (HP03)2or  2HPO3. 

Phosphoric        water.  Glacial  phosphoric  acid, 

anhydride. 


182  DENTAL    CHEMISTRY. 

266.  Hydrogen  Phosphate  or  Phosphoric 
Acid.— 

There  are  several  kinds  of  phosphoric  acid, 
but  we  shall  here  speak  of  two  only: — 
I.    Common  Phosphoric  Acid— * 

Synonyms:  tri-basic  phosphoric  acid,  tri- 
hydrogen  phosphate;  (it  is  sometimes  called 
ortho-phosphoric  acid). 

Theoretical  constitution:  H3PO4:  may  be 
regarded  as  mono-meta-phosphoric  acid,  i.  e., 
the  acid  obtained  by  removing"  one  molecule 
of  water  from  ortho-phosphoric^'  acid.  Ortho- 
phosphoric  acid  has  for  its  formula  HgPOs, 
which  formula  minus  H2O  becomes  H3PO4, 
rationally  (PO)"'(HO)3.  The  acid  contains, 
then,  three  atoms  of  hydrogen,  one  of  phos- 
phorus, and  four  of  oxygen;  by  weight  3  parts 
hydrogen,  31  of  phosphorus,  64  of  oxygen. 
Molecular  weight,  98.  Its  salts  are  jyhos- 
phatesf'* 

Preparation:  made  by  boiling  phosphorus 
in  dilute  nitric  acid,  and  evaporating  to  a 
syrupy  liquid. 

Properties:    syrupy   liquid,   which,   if  evap- 

*  Phosphoric  acid  is  tri-basic,  and,  therefore,  three  hydroxyl 
groups  are  assumed  to  be  present  in  it,  hence  the  rational  formula 
is  PO  (H0)3.     The  graphic  formula  is  probably 

/OH 
PO    -  OH 

\0H 

**  Called  often  ortho-phosphates. 


INORGANIC   CHEMISTRY.  183 

orated  spontaneously  over  sulphuric  acid,  gives 
hard,  transparent,  prismatic  crystals  readily 
deliquescing.     It  does  not  coagulate  albumin. 

Acidum  Phosplioricum,  U.  S.  P.,  is  a  color- 

-less,  strongly  acid  liquid  of  sp.  gr.  1.347.     It 

does  not  fume  and  should  not  contain  arsenic. 

It  contains  50  per  cent,  acid  to  50  of  water. 

It  is  odorless. 

Acidum  Pliosphoricum  Diliituiii,  U.  S.  P., 
contains  10  per  cent,  of  H3PO4,  and  is  com- 
posed of  I  part  of  Acidum  Phosphoricum,  to  4 
of  distilled  water. 

5jr///3' phosphoric  acid:  H3PO4,  syrupy  phos- 
phoric acid,  contains  on  an  average,  about  66 
per  cent,  of  H3PO4,  and  as  sold  by  manufac- 
turing chemists  is  not  the  glacial  acid  but 
merely  a  strong  phosphoric  acid  of  syrupy 
consistence.  It  is  of  different  strengths  ac- 
cording to  the  makers. 

2.    Olacial  Pliosplioric  Acid. 

Synonyms:  mono-hydrogen  phosphate, 
meta-phosphoric  acid,  di-meta-phosphoric 
acid,  mono-hydrated  phosphoric  acid. 

Theoretical  constitution:  HPO3  or  di-meta- 
phosphoric  acid,  /.  e.,  derived  by  subtracting 
two  molecules  of  water  from  ortho-phosphoric* 
acid.  H5PO5  —  2H2O  ==  HPO3.  Its  molecule, 
therefore,  consists  of  i  part  hydrogen,  i  part 

*  Not  what  is  usually  called  ortho-phosphoric  acid,  but  the  maxi- 
mum hydroxide  or  normal  acid  of  phosphorus. 


184  DENTAL   CHEMISTRY. 

phosphorus,  and  3  parts  oxyg-en ;  by  weig^ht  i 
part  hydrogen,  31  of  phosphorus,  and  48  of 
oxygen.     Molecular  weight,  80. 

Preparation:    it  may  be    made  by  heating 
the  ordinary  acid,  which  loses  a  molecule   of 
water  and  becomes  the  glacial  acid. 
.        H3PO,    =     HPO3      -h     H,0 

Phosphoric  acid.       Glacial  phosphoric  acid.  Water. 

It  is  sometimes  made  by  calcining  ammo- 
nium phosphate,  but  the  product  is  then  likely 
to  contain  ammonia.* 

Properties:  on  cooling  the  platinum  vessel 
in  which  the  common  acid,  H3PO4,  has  been 
heated  to  redness,  a  vitreous  mass,  HPO3,  is 
seen,  hard,  colorless,  transparent,  not  crystalli- 
zable,  readily  soluble  in  water,  forming  an  in- 
tensely acid  solution  which  is  slowly  converted 
into  the  ordinary  acid.  It  coagulates  albumin. 
In  commerce  it  comes  in  the  form  of  sticks  or 
brittle  cakes,  odorless,  sour  to  the  taste  and 
hygroscopic,  more  or  less  contaminated  with 
pyro-phosphoric  acid,  and  containing*  phos- 
phates of  sodium,  calcium,  magnesium,  etc. 
Solution  of  the  common  acid  in  water  when 
heated  becomes  first  pyro-phosphoric  acid, 
then  (at  red  heat)  glacial  phosphoric  acid. 

Use  in  dentistry:  the  dilute  acid  is  used  as 

*  The  formation  of  meta-phosphoric  acid  from  ordinary  phosphoric 
acid  is  represented  thus: — 

(^  (  O 

OH  '  *^ 


i8r''isH+"'° 


INORGANIC   CHEMISTRY. 


185 


a  local  application  in  caries,  and  has  been 
given  internally.  It  is  liable  to  fungoid  growth 
of  a  tenacious  or  mucoid  character,  diffusible, 
and  of  a  yellowish-gray  color;  it  loses  strength 
on  development  of  this  growth,  its  specific 
gravity  falling  often  below  1055. 

Table  2.1 — Phosphoric  Acids, 
common  phosphoric     glacial  phosphoric 


ACID. 

H3PO4.        Called    by 
some       ortho-phos- 
phoric acid. 
Syrupy  liquid. 

Evaporated  spontane- 
ously yields  pris- 
matic crystals. 

Does  not  coagulate 
albumin. 

Strong  acid  is  called 
syrupy  phosphoric 
acid. 

The  official  acid  (50 
per  cent.)  heated 
above  392°  F.  is  con- 
verted gradually  into 
the  glacial  acid  and 
pyrophosphoricacid. 

Little  or  no  precipitate 
with  solution  of  sil- 
ver nitrate. 


ACID. 

HPO3.    Called  meta- 
phosphoric  acid. 
Solid. 

Does  not  crystallize, 
but  forms  an  amor- 
phous, glassy  mass, 
coagulates  albumin. 

Slowly  turns  into  the 
common  acid. 

Is  volatile  at  red  heat, 
and  when  boiled 
with  water  is  con- 
verted into  the  com- 
mon acid. 

Abundant  precipitate 
with  solution  of  sil- 
ver nitrate. 


*  Rollins  obtains  it  as  a  soft  solidby  the  process  given  in  section  201. 
It  is  said  {Zeitschrift  f.  anal.  CJicmie.,  VI.  187,)  that  really  pure  phos- 
phoric acid  makes  a  soft  glutinous  mass  when  heated,  but  on  heating 
strongly  for  seven  or  eight  minutes  after  the  acid  has  begun  to  go 
ofif  in  white  fumes  a  hard  mass  is  obtained. 


186  DENTAL    CHEMISTRY. 

267.  Nitrogen. 

Symbol:  N.  Atoms  in  molecule:  N2.  Atomic  weight:  14. 
Molecular  weight:  28.  Dejisity:  14.  Specific  gravity:  0.971, 
(air=i).  Weight  of  one  litre  of  gas:  1.256  grammes. 
Solubility  in  water:  i  part  of  water  dissolves  0.025  part  by 
volume  of  nitrogen. 

Occurrence  in  nature:  nitrogen  constitutes  79.07  per 
cent,  by  volume  of  atmospheric  air. 

How  made:  obtained  from  air  by  burning  phosphorus 
in  a  confined  space. 

Properties:  affinity  for  magnesium,  borum,  vanadium, 
titanium.  Very  inert  chemically.  Colorless,  tasteless, 
odorless,  transparent  gas.  Incombustible  and  does  not 
support  combustion.  In  combination  found  in  nitro- 
glycerine, poisonous  alkaloids  as  strychnine,  and  in  albu- 
minoid substances. 

268.  Ammonia. 

Theoretical  constitution:  H3N  or  NH3,  one  atom  of 
nitrogen  to  three  of  hydrogen;  by  weight,  14  parts  nitro- 
gen to  3  of  hydrogen.  Molecular  weight,  17;  density, 
8.5;  specific  gravity,  0.59  (air  =  i). 

Origin  and  method  of  preparation:  it  is  a  product  of 
the  putrefaction  of  animal  matters.  Artificially  it  may 
be  prepared  by  heating  sal-ammoniac  and  quicklime. 

Properties:  colorless  gas,  pungent  odor,  strongly  alka- 
line, extraordinarily  soluble  in  water,  11 49  volumes  of  the 
gas  in  I  of  water.     Very  volatile. 

269.  Nitrogen  Monoxide  or  Laugliing  Gas. 

Synonyms:  hyponitrous  oxide,  nitrous  oxide, 
nitrogen  protoxide. 

Discovered  by  Priestly  in  1776;  first  came 
into  notice  as  anaesthetic  in  1863;  first  used 
in  dentistry  by  Wells  of  Hartford,  in  1845. 

Theoretical  constitution:    N2O,  hyponitrous 


INORGANIC   CHEMISTRY.  J^g^ 

oxide  or  nitrogen  monoxide;  univalent  nitro- 
gen with  bivalent  oxygen — two  atoms  of  nitro- 
gen with  one  of  oxygen;  composition  by  vol- 
ume, 2  parts  of  nitrogen  to  i  of  oxygen;  by 
weight,  28  parts  of  nitrogen  to  16  of  oxygen. 
Molecular  weight,  44.  Density,  22.  Sp.  gr., 
1.527.    Weight  of  a  litre,  1.98  gramme. 

Preparation:  made  by  cautiously  heating 
ammonium  nitrate,  which  is  decomposed, 
yielding  laughing  gas  and  water: 

NH.NOa    =    N2O    +    2H2O 

Ammonium  nitrate.  Nitrogen  protoxide.      Water. 

Properties:  colorless,  odorless,  sweetish- 
tasting  gas  of  neutral  reaction,  soluble  in 
water  100  volumes  of  which  dissolve  78  vol- 
umes of  the  gas,  more  soluble  in  alcohol. 
Supports  combustion,  the  heat  of  burning 
bodies  decomposing  it  and  setting  oxygen 
free.  Condenses  to  a  colorless  liquid  under 
pressure  of  50  atmospheres  and  temperature 
of  45°F.,  specific  gravity  of  the  liquid,  0.908. 
Boiling  point, — i26°F.,  freezing  point, — I50°F. 

When  inhaled  it  causes  exhilaration,  anaes- 
thesia, and  finally  asphyxia.  It  dissolves  in 
the  blood  without  entering  into  combination 
with  it,  and  its  action  seems  to  be  due  partly 
to  its  excluding  air  and  partly  to  its  direct 
effect  on  the  nervous  system.  The  anassthesia 
produced  by  it  is  of  short  duration  and  with- 
out an  excitement  stage.     The  sensation  is 


]^88  DENTAL    CHEMISTRY. 

usually  one  of  agreeable  intoxication;  dis- 
agreeable after-effects  are  generally  wanting. 
Lyman  holds  that  the  anaesthesia  is  a  narcosis, 
but  Wallian  thinks  with  Ziegler  that  it  is  not 
merely  an  asphyxiating"  agent. 

Use  in  dentistry:  as  a  temporary  anaesthetic. 
Out  of  121,  709  administrations  of  the  g'as  re- 
corded from  1863  to  1 88 1,  there  was  not  one 
which  resulted  fatally,  nor  produced  serious 
ill-effects. 

For  anaesthetic  purposes  the  nitrogen  mon- 
oxide is  liquefied  and  sold  in  wrought-iron 
cylinders  provided  with  a  stop-cock,  on  turn- 
ing; which  the  liquid  is  vaporized,  and  may  be 
collected  in  rubber  gas  bags  or  small  gasome- 
ters. When  the  gas  is  to  be  administered  it 
may  be  inhaled  from  the  g"as  bag;  or  g:aso- 
meter  through  a  rubber  tube  and  mouth-piece 
provided  for  the  purpose.  The  advantag:es  of 
the  cylinder  are  that  the  g"as  may  be  kept  for 
any  length  of  time  without  loss  of  strength  or 
volume. 

270.    Hydrogen  IS^itrate  or  Nitric  Acid.— 

Synonyms:  hydric  nitrate,  Glauber's  spirits 
of  nitre,  spirits  of  nitre,  fuming  spirits  of  nitre, 
aqua  fortis,  azotic  acid.  Official  name,  Acid- 
um  Nitricum. 

Known  to  the  Arabs  in  the  9th  century. 
Theoretical  constitution:   HNO3,  an  ox-acid 
whose  molecule  is  composed  of  i  atom  of  hy- 


INORGANIC   CHEMISTRY.  189 

drog-en,  i  of  nitrogen,  and  3  of  oxygen.  By 
volume  it  consists  of  i  part  of  hydrogen,  i  of 
nitrogen,  and  3  of  oxygen.  By  weight,  i  part 
of  hydrogen,  14  of  nitrogen,  48  of  oxygen. 
Molecular  weight,  63. 

Preparation:   made  by  decomposing  potas- 
sium nitrate  (nitre)  with  sulphuric  acid: 
KNO3  +  H,SO,  =  KHSO4  +  HNO3 

Potassium  Sulphuric  Potassium  acid  Nitric 

Bitrate.  acid.  sulpliate.  acid. 

Properties:  the  pure  acid  is  a  colorless,  fum- 
ing, corrosive,  rather  heavy,  strongly  acid 
liquid  of  sp.  gr.  1.52.  The  official  acid  has  a 
specific  gravity  of  1.42,  and  contains  69.40  per 
cent,  of  absolute  acid  to  30.60  per  cent,  of 
water.  Exposed  to  air  and  light  it  is  decom- 
posed and  becomes  yellow.  Nitric  acid  dis- 
solves mercury,  copper,  silver,  and  bismuth, 
especially  when  warmed;  dilute  nitric  acid  dis- 
solves iron,  lead,  and  silver.  Antimony  and 
tin  are  attacked  by  the  acid  and  oxidized,  but 
not  dissolved.  Nitric  acid  has  no  action  on 
gold,  platinum,  or  iridium.  It  attacks  and 
destroys  vegetable  and  animal  tissues,  pro- 
ducing a  yellow  discoloration,  especially  on 
animal  matters  and  products.  Its  stain  on 
clothing  can  not  readily  be  removed  but 
ammonia  prevents  destruction  of  the  cloth.  Its 
salts  are  nitrates. 

Acidiim  Nitrictim  Dilutum  is  one  part  of 
the  official  acid  to  six  of  distilled  water.     Its 


190  DENTAL   CHEMISTRY. 

sp.  gr.  is  1.059,  3-i^d  it  contains  ten  per  cent,  of 
HNO3. 

Use  in  dentistry:  mixed  with  four  parts  of 
hydrochloric  acid,  it  is  used  to  dissolve  g'old. 
[The  official  mixture  is  four  parts  nitric  acid 
by  weig^ht,  to  15  of  hydrochloric  acid,  and  is 
called  Acidum  Nitrohydrochloricum]. 

Nitric  acid  is  also  used  to  dissolve  zinc 
oxide  in  the  preparation  of  the  oxyphosphate 
cement.  It  is  used  in  dental  medicine  as  a 
caustic.  It  attacks  the  teeth,  and  hence,  when 
used  in  any  form  in  the  mouth,  care  should  be 
taken  that  it  does  not  touch  other  tissues  than 
the  ones  to  which  it  is  applied. 

Toxicology:  nitric  acid  is  a  violent  poison 
turning-  the  mucous  membranes  a  bright  yel- 
low and  then  corroding  them.  The  mitidotes 
are  alkalies  or  magnesia  suspended  in  water, 
sodium  bicarbonate  in  water,  soap  and  water; 
bland  liquids  should  be  given  and  the  patient's 
strength  sustained.  Burns  should  be  treated 
like  those  from  hydrochloric  acid.  (See  section 
181). 


INORGANIC   CHEMISTRY.  191 

Tetrads. 

271.     The  following  is  a  list  of  important  tetrads: 

Table  23.    Tetrads. 

Aluminium.* 


Cerium.* 
Tin. 


Tetrads 
positive 


Palladium.  [        to 

Platinum.  j  hydrog^en. 

Iridium.  J 


Silicon. 

Titanium. 

Carbon. 


Tetrads 
negative 

to 
hydrog'en. 


272.    Aluminium. — 

Symbol:  Al.  Lathi  name:  Aluminium  or  Aluminum. 
Equivalence:  IV  and  (Alg)".  Specific  gravity:  2.50102.67. 
Atomic  weight'.  27.  Revised  atomic  weight:  27.009.  Electri- 
cal state:  +•  Fusing  point:  I292°F.  Length  of  bar:  etc.: 
1.0022  (5th  rank).  Wt.  of  cubic  ft.  in  lbs.:  166.8.  Tensile 
strength;  12.  Tenacity:  like  silver.  Malleability:  like  silver 
and  gold.  Ductility:  'j'.i^'j'OarzxvV.^.  Co7iducti7ig pozver  {heat): 
4;  (4th  rank).  .Conducting  power  {electricity):  better  than 
that  of  iron.  Resistance  to  air,  etc.:  tarnishes  very  slowly; 
not  affected  by  sulphuretted  hydrogen.  Solubility:  solu- 
ble in  hydrochloric  acid,  and  in  aqueous  solutions  of 
alkaline  hydrates;  resists  cold  acids,  mineral  and  vegeta- 
ble (except  hydrochloric).  Direct  combitiations:  with 
many  metals  and  non-metals.  Does  not  oxidize;  is  not 
attacked  by  sulphur  compounds.  Color  and  appearance: 
bluish  white,  brilliant.  Structure :  octahedral  crystals. 
Consistence:    hard    as    zinc.     Very    sonorous.     Compounds: 

*  Both  aluminium  and  cerium  appear  to  be  trivalent,  but  are  really 
quadrivalent  like  the  ferric  compounds. 


192  DENTAL   CHEMISTRY. 

two  atoms  with  equivalence  of  six  like  ferric  salts.  Alloys: 

aluminium  bronze,  solder,  etc.     Does  not  amalgamate. 

Use  in  dentistry:  for  making  "  plates." 

Occurrence:  the  great  mass  of  the  earth  is  composed 

of  aluminium,  in  combination  with  silicic  acid,  in  silicated 

rocks,    such    as    granite,    feldspar,    basalt,    slate,    mica, 

etc.,   and  in  the  various  modifications  of  clay.      Every 

variety  of  clay  contains  it  in  quantity  varying  from  12  to 

20  per  cent.*    The  minerals  known  as  corundum,  ruby, 

sapphire,  and  emery  are  aluminium  oxide  in  crystallized 

state. 

Preparation:  the  usual  process  for  obtaining  aluminium 

has  been  to  decompose  the  chloride  by  metallic  sodium: 

Al.,Cle    +     6Na    =    6NaCl     +     2AI 

It  will  be  noticed  that  aluminium  acts  as  a  pseudo-triad, 
(AI2)''*,  in  the  chloride  of  aluminium. 

The  process  is  that  of  Deville.  At  the  works  of  Morin 
in  Paris,  ten  parts  sodio-aluminium  chloride,  five  parts  of 
fluorspar  or  cryolite,  and  two  parts  of  sodium,  are  mixed 
together  and  thrown  upon  the  hearth  of  a  reverberatory 
furnace,  previously  heated  to  full  redness.  A  violent 
action  takes  place,  great  heat  is  evolved,  and  the  lique- 
fied mass  of  slag  and  metal  collects  at  the  back  of  the 
furnace.     The  latter  is  drawn  off  and  cast  into  ingots. 

Metallic  sodium  is  very  troublesome  to  handle,  and  its 
cost  has  been  so  high  that  the  price  of  aluminium  has 
been,  in  consequence  of  the  difficulty  and  expense  of  the 
process,  higher  per  troy  ounce  than  that  of  silver.  Re- 
cent improvements  in  process  have  been  made  in  this 
country;  one  is  to  reduce  the  aluminous  materials  with 
sodium  vapor,  and  to  use  the  double  fluoride  of  aluminium 
and  sodium,  or  double  chloride  of  aluminium  and  sodi- 
um,  made   at   reduced  cost;    another   is  to  prepare  the 

*  The  sapphire  and  ruby  contain  also  a  little  oxide  of  iron  ;  emery 
contains  oxide  of  iron  and  also  silica. 


INORGANIC   CHEMISTRY.  193 

metal  electrolytically;*  another  to  reduce  the  aluminous 
earths  with  zinc  ore.  The  price  will  probably  be  greatly 
reduced  before  long.  Metallic  magnesium  has  been  re- 
duced to  one-fifth  of  its  previous  price,  and,  as  this  sub- 
stance also  is  used  in  manufacture  of  aluminium,  it  will, 
probably,  affect  the  price  of  the  latter.f 

273.  Value  in  dentistry  and  in  the  arts:J  aluminium  is 
remarkable  for  its  resistance  to  the  air,  and  for  its  great 
lightness.  It  is  said  to  be  stronger  than  steel.  It  is  four 
times  lighter  than  silver,  and  seven  or  eight  times  lighter 
than  platinum.  Gas  fumes  and  sulphur  do  not  tarnish  it. 
It  is  whiter  than  nickel,  and  makes  a  fine  substitute  for  silver. 
Alloyed  with  silver  and  copper,  it  gives  a  non-tarnishing 
and  non-corrosive  quality  to  these  metals,  and  greatly  in- 
creases their  tensile  strength.  Aluminium  bronze  is  com- 
posed of  10  pounds  of  aluminium  to  90  pounds  of  copper, 
and  has  a  tensile  strength  of  three  tons  per  square  inch 
greater  than  Bessemer  steel.  A  solder  has  been  invented 
which,  it  is  claimed,  will  enable  aluminium  to  be  welded. 
[An  alloy  of  aluminium  and  tin  has  been  used,  10  parts  tin 
to  100  of  aluminium,  for  internal  parts  of  instruments,  as 
electrical  instruments.  The  apex  of  the  Washington 
Monument  is  of  aluminium;  its  surface  appears  much 
whiter  than  silver,  and  is  so  highly  polished  as  to  resem- 
ble a  plate  glass  mirror]. 

*  The  Cowles  method  consists  in  passing  a  powerful  electric 
current  through  a  mixture  of  mineral  copper  and  carbon.  A  high 
temperature  is  obtained  by  which  the  mineral  is  reduced  by  the 
carbon. 

t  The  Netto  process  involves  the  use  of  ingots  of  sodium. 

J  When  aluminium  is  to  be  melted  to  make  a  casting,  for  instance, 
this  must  not  be  done  in  clay  crucibles,  since  it  reduces  the  silica 
contained  therein  to  silicium,  whereby  it  becomes  gray  and  brittle. 
It  must  be  melted  in  lime  crucibles  ;  or  if  clay  crucibles  are  used, 
they  must  be  lined  with  carbon  or  well-ignited  cryolite.  Graphite 
crucibles,  however,  are  the  best. 


194 


DENTAL   CHEMISTRY. 


In  prosthetic  dentistry  the  use  of  aluminium 
has  been  urged,  on  the  ground  (i)  that  it  is 
the  only  metal  which  can  be  used  ;^iire  and 
unalloyed  in  the  manufacture  of  plates,  (2)  that 
it  is  the  lightest  of  the  metals  available  for 
such  a  purpose.  It  is  claimed  by  some  that 
aluminium  is  unalterable  in  the  mouth,  and 
does  not  irritate  the  gums,  hence  is  superior  to 
caoutchouc.  It  is  thought,  therefore,  that  it 
will  replace  gold  and  platinum  in  prosthetic 
dentistry .■^'  According  to  Palmer  there  is  little 
or  no  galvanic  action  in  the  oral  cavity  when 
aluminium  is  used;  a  carpet  tack  may  be  held 
in  the  mouth,  in  contact  with  the  aluminium, 
without  unpleasant  sensation. 

274.    Alloys  of  Aluminium.— 

Aluminimn  solder  is  6  parts  aluminium,  4  copper,  90  zinc. 
Others  have  been  devised  as  follows: 


No.  1. 

No.  2. 

No.  3. 

Zinc 

80 

8 

12 

85 
6 
9 

88 

Copper          

5 

Aluminium 

7 

*  Some  have  claimed  that  it  is  gradually  attacked  by  articles  used 
in  diet,  such  as  vinegar  and  solutions  of  comm,on  salt,  and  by  alka- 
line solutions.  Chandler's  objection  to  its  use  is  the  difference  in 
expansion  between  it  and  the  vulcanite  used  in  fastening  the  teeth. 
The  heat  of  the  mouth,  hot  drinks,  etc.,  etc.,  cause  a  separation. 
Carbonate  of  lime  is  deposited  from  the  saliva  in  the  opening,  until 
finally  the  space  is  perceptible  to  the  tongue. 


INORGANIC    CHEMISTRY.  195 

Aluminium  may  be  soldered  by  coating  it  with  copper 
as  in  electrotyping,  then  soldering  as  usual.* 

275.    Compounds  of  Aluminium.— 

Alums: 

Theoretical  constitution:  alums  are  what  are  known  as 
"  double  salts."  They  are  formed  by  the  combination  of 
aluminium  sulphate  with  other  sulphates.  The  formula 
for  aluminium  sulphate  is  (  Al2)2  (S04)6  or  Alg  (804)3,  alum- 
inium being  a  pseudo-triad.  The  formula  for  potas- 
sium sulphate  is  K2SO4,  for  ammonium  sulphate  (NH4)2 
SO4.  The  formula  for  potash  alum  or  potassium  and 
aluminium  sulphate  is  K2Al2(S04)4,  that  is  K2(S04)  + 
Al2(S04)3.  Ammonia  alum  is  (NH4)2Al2(S04)424H20. 
Ferric  alum  contains  no  aluminium  at  all,  but  is  the  double 
sulphate  of  ammonium  and  ferric  iron,  thus  (NH4)2Fe2 
(504)4.241^20-      The  ofificial   alum  is  potash-alum,  K2Alg 

(S04)4.24H.20. 

Official  name :  Aluminii  et  Potassii  Sulphas. 

Preparation  and  properties:  alum  is  manufactured,  on  a 
large  scale,  by  decomposing  various  silicates  of  alumin- 
ium with  sulphuric  acid,  aluminium  sulphate  being 
formed.  To  this  is  added  solution  of  potassium  sul- 
phate, if  potash  alum  be  desired,  or  ammonium  sulphate, 
if  ammonia  alum  is  sought.  On  evaporation  the  alum 
crystallizes. 

Potash  alum  occurs  in  form  of  regular  octahedral  crystals, 
white,  efflorescent,  soluble  in    10  parts  of  cold  water  and 

*  A  good  solder  for  aluminium  is  said  to  be  made  by  melting  to- 
gether 0  parts  of  zinc,  2  parts  of  tin,  and  1  part  of  lead,  and  rolling 
this  out  into  thin  sheets.  The  aluminium  surface  to  be  soldered 
must  be  scraped  clear  of  all  oxide,  and  coated  with  paraffin.  A 
piece  of  the  solder  is  then  placed  upon  each  portion  and  heated 
This  causes  the  paraffin  to  melt ;  on  further  heating  the  solder  melts 
and  unites  with  the  aluminium.  The  two  surfaces  thus  coated  are 
then  soldered  together  in  the  usual  manner. 


196  DENTAL   CHEMISTRY. 

0.3  parts  boiling,  insoluble  in  alcohol;  its  solution  has  an 
acid  reaction  and  an  astringent,  sweetish  taste.  By- 
heating  for  several  days  at  a  temperature  of  I76°F.,  the 
water  of  crystallization  is  expelled  and  it  becomes  dried 
alum,  Alumen  exsiccatum.  Alum  is  used  in  dentistry 
as  an  astringent,  styptic,  and,  in  connection  with  Labar- 
raque's  solution,  as  a  bleaching  agent. 

Aluminium  chloride:  this  substance,  AlgCle,  comes  in 
colorless,  deliquescent  crystals,  very  soluble  in  water,  of 
a  sharp  saline  taste,  antiseptic,  disinfectant.  It  is  made 
by  passing  chlorine  gas  over  a  mixture  of  charcoal  and 
alumina  at  bright  red  heat: 

AI2O3    +     3C.    +     6C1     =     3CO     +     Al,Cle 

Alumina  carbon  chlorine  carbon  aluminium 

monoxide  cliloride 

It  has  been  used  to  bleach  discolored  teeth. 

The  substance  called  Choralum  contains  the  chloride  of 
aluminium. 

Aluminium  permanganate:  this  substance  is  said  to 
be  a  constituent  of  some  disinfecting  solutions. 

Aluminium  silicates:  there  are  many  silicates  of  alu- 
minium. Clay  is  a  hydrated  silicate,  usually  mixed  with 
excess  of  silica.  Purer  kinds  of  clay  are  derived  from 
feldspar  of  the  formula,  AI2O3K2O,  6Si02.  On  exposure 
to  air  the  silicate  of  aluminium  alone  remains,  the  alka- 
line silicates  washing  away.  Earthenware,  bricks,  and 
pottery  are  made  from  clay,  porcelain  and  the  better  kinds 
of  stoneware  from  the  purest  clay,  and  glazed  with  feld- 
spar. Firebricks,  crucibles,  arid  the  like  are  prepared 
from  pure  varieties  of  clay,  free  from  lime,  magnesia,  or 
iron,  but  j:ontaining  a  large  proportion  of  silica.  Com- 
mon clays  have  the  formula,  Al203.2Si02;  some  kinds  of 
fire  clay,  Al203.6Si02.  Silicate  of  aluminium  is  an  ingre- 
dient of  hydraulic  cement. 

Alumina  is  an  oxide,  AI2O3.  Corundum  and  emery  are 
nearly  pure  alumina. 


INORGANIC   CHEMISTRY.  197 

276.  Artificial  teetli:  teeth  are  composed 
of  two  portions,  the  body  or  base  and  the 
enamel.  The  constituents  of  the  body  are 
chiefly  silex,  feldspar,  and  kaolin.  The  en- 
amel is  composed  principally  of  feldspar. 
Coloring  matters  are  also  used,  and  consist  of 
various  metals,  in  a  state  of  minute  division,  or 
of  metallic  oxides. 

277.  Feldspar  is  a  double  silicate  of  alumin- 
ium and  potassium,  its  composition  being 
represented  by  the  formula,  KaSigO?,  AlaSisOg. 
It  also  contains  lime  and  oxide  of  iron.  It  is 
prepared  for  dental  uses  in  the  same  way  as 
silex.     It  is  readily  fusible. 

278.  Kaolin  is  essentially  a  silicate  of  alu- 
minium. It  usually  contains  oxide  of  iron  and 
some  other  substances,  as  magnesia,  potash, 
etc.,  etc.  It  is  the  result  of  the  decomposition 
of  feldspar.  Relatively  large  proportions  of 
kaolin  give  teeth  an  opaque  and  lifeless  ap- 
pearance; modern  mineral  teeth  contain  less 
kaolin  and  more  feldspar.  It  is  prepared  for 
dental  uses  by  washing,  letting  settle,  decant- 
ing, letting  settle,  decanting  again,  and  drying 
in  the  sun. 

279.  Crown  enamels  are  composed  of  feld- 
spar, as  a  basis,  with  various  coloring  matters, 
such  as  titanium,  spongy  platinum,  oxide  of 
gold. 

280.  The  dry  metliod  of  preparation  of 


198  DENTAL   CHEMISTRY. 

gum-enamel  as  practised  by  Wildman  and 
described  by  Essig,  is  divided  into  three 
stages :  first,  the  preparation  of  the  oxide ;  second, 
fritting",  or,  by  aid  of  heat,  uniting-  the  metalhc 
oxide  with  a  sihcious  base;  and,  third,  diluting 
the  frit  so  as  to  form  the  desired  shade.  In 
this  method  the  purple  of  Cassius  (metallic 
oxide)  is  prepared  in  the  dry  way  by  fusing 
silver,  gold,  and  tin  with  borax,  removing 
borax  glass  formed,  dissolving  the  silver  with 
nitric  acid,  washing  well  and  drying.  The  frit 
is  formed  by  mixing  the  purple  of  Cassius 
thus  made  with  a  flux  composed  of  quartz, 
borax  glass,  and  sal  tartar.  Lastly,  the  frit  is 
diluted  with  the  proper  amount  of  feldspar. 

281.  Cerium. — 

Symbol:  Ce.  Latin  name:  Cerium.  Eqnivale7icc:  II  and 
IV.  Specific  gravity.  6.62.  Atomic  zveight  (approx. ): 
140.4.   Atomic  weight  [revised):  140.424.   Electrical  state:  +• 

The  most  important  compound  is  the  oxalate.  (Sec- 
tion 435). 

282.  Tin.— 

Symbol:  Sn.  Lati7i  name:  Stannum.  Eqtiivalencc:  II 
and  IV.  Specific  gravity:  7.29  to  7.30.  Atomic  weight: 
1 17.7.  Revised  weight:  117.698.  Electrical  state:  -\-.  Fus- 
ing point:  4420F.  (According  to  some,  458.6°F.)  Length 
of  bar  at  21 2P:  1.0023;  (4th  rank).  Weight  of  cubic  feet  in 
lbs.:  455.1.  Tensile  strength:  2  to  3.5.  Tenacity:  1.33  com- 
pared with  lead;  (9th  rank).  Malleability:  4;  (4th  rank). 
Ductility:  9;  (9th  rank).  Conductijig pozuer  {heat):  7;  (7th 
rank).  Co^iducting pozver  {electricity):  83,  (silver  ^  1000); 
(9th   rank).     Resistance  to  air,  etc.:  3;  (3d   rank).     Solu- 


INORGANIC   CHEMISTRY.  .      JQQ 

bility:  soluble  in  dilute  acids  and  alkalies.  Resists  cor- 
rosion of  air,  water,  etc.,  better  than  iron  or  copper. 
Nitric  acid  converts  it  into  metastannic  acid.  Dissolved 
in  hydrochloric  acid,  stannous  chloride  is  formed.  In 
aqua  regia,  stannic  chloride.  Direct  combinations:  with 
oxygen  When  strongly  heated,  sulphur,  chlorine.  It  does 
not  combine  chemically  with  mercury.  Color  and  appear- 
ance', white,  brilliant.  Structure:  crystalline  in  two  sys- 
tems, isometric  and  quadratic.  Consistence:  soft.  Com- 
pounds: stannic  (equivalence  IV)  and  stannous  (equiva- 
lence II).  Alloys:  pewter,  brittania,  queen's  metal,  solder, 
bell-metal,  gun-metal,  bronze,  speculum  metal,  fusible 
metals,  sterro-metal,  type  metal. 

Occurrence:  tin  occurs  chiefly  in  form  of 
tinstone,  stannic  oxide,  SnOa.  The  ore  is 
found  in  Cornwall,  Australia,  Bohemia,  Sax- 
ony, Malacca,  Banca,  Siberia,  Sweden,  North 
and  South  America.  Tin  obtained  from  Ma- 
lacca and  Banca  is  known  as  straits  tin,  and  is 
of  great  purity.  The  tin  deposits  of  New 
South  Wales  cover  an  area  of  over  5,000,000 
acres;  tin  ore  is  also  very  abundant  in  Queens- 
land. In  the  United  States  tin  ore  has  been 
found  in  West  Virginia  and  adjoining"  parts 
of  Ohio,  in  North  Carolina,  and  in  the  far 
West,  as  in  Utah,  Dakota. 
,  Preparation:  the  metal  is  easily  obtained 
from  the  ore  by  heating  the  latter,  after  purifi- 
<:ation,  with  coal: 

2Sn02    +     2C2    ==    Sn2    +     4CO 

Stannic  Carbon  Tin  Carbon 

oxide  mon-oxide 

283.    Pttre  tin,  in  crystalline  form,  may  be 


200  DENTAL    CHEMISTRY. 

thrown  down  by  introducing  a  plate  of  tin  into  a 
strong  solution  of  stannous  chloride,  on  which 
water  is  floated.  Another  method  by  which 
tin,  entirely  pure,  may  be  obtained  is  by  evap- 
orating a  solution  of  stannous  chloride  to 
small  bulk,  and  oxidizing  by  addition  of  nitric 
acid.  Stannic  oxide  is  obtained,  which,  after 
washing  and  drying,  is  exposed  to  a  red  heat 
in  a  crucible  with  charcoal. 

284.  Tin  in  dentistry:  tin  amalgamates 
readily  with  mercury,  and  in  most  cases  there 
is  condensation.  Pure  tin  in  form  of  foil  is 
used  as  a  filling,  and  also  in  connection  with 
non-cohesive  gold. 

285.  Alloys  of  tin.— 

Pewter  is  an  alloy  of  variable  composition,  usually  tin, 
lead,  copper,  and  antimony  or  zinc.  Plated  pewter  is  7 
antimony,  2  bismuth,  2  copper,  89  tin.  A  pewter  often 
used  is  tin,  92,  lead,  8. 

Rees's  alloy  is  tin  20,  gold  i,  silver  2. 

Common  Solder  is  an  alloy  of  tin  and  lead.  [Fine 
solder  is  33.3  lead  to  66.6  tin.  Common  solder  is  equal 
parts  tin  and  lead;  coarse  solder  is  66.6  lead  to  33.3  tin]. 

286.  Compounds  of  tin.— 

stannous  Chloride : 

This  substance,  known  to  the  dyer  as  "  tin  salt,"  is 
made  by  dissolving  metallic  tin  in  hydrochloric  acid.  It 
may  also  be  prepared  by  distilling  tin  filings  with  mer- 
curous  chloride.  Its  formula  is  SnCl2,2H20;  molecular 
weight,  224.5,  It  is  used  locally.  It  is  poisonous;  the 
antidotes  are  baking  soda,  magnesia,  milk,  and  white  of 
egg.     Tin   dissolved    in    nitrohydrochloric    acid    yields 


INORGANIC   CHEMISTRY.  201 

stannic  chloride,  SnC^.  The  two  chlorides  of  tin  in  con- 
nection with  auric  chloride  yield  purple  of  Cassius.  (See 
section  258.) 

287.  Palladium.— 

Symbol:  Pd.  Lati7i  name:  Palladium,  Equivalence:  II 
and  IV.  Specific  gravity :  11. 80.  Atomic  weight:  106.  Re- 
vised atomic  weight:  105.737.  Electrical  state:  +•  Fusing 
point:  lower  than  platinum,  but  requires  oxy-hydrogen 
blow-pipe.  Length  of  bar,  etc.:  i.ooio;  (12th  rank).  Wt. 
of  cubic  ft.  VI  lbs.:  736.6.  Tenacity:  11^  (Lead  =  1):  (7th 
rank).  Malleability:  inferior  to  platinum.  Ductility:  6; 
(6th  rank).  Conducting  power  {electricity):  184  (silver  = 
1000);  (5th  rank).  Resistance  to  air,  etc.:  i;  (first  rank). 
More  oxidizable  than  platinum  at  red  heat.  Solubility: 
soluble  in  nitric  acid;  attacked  by  iodine;  aqua  regia  best 
solvent.  Direct  combinations:  cyanogen,  iodine,  hydrogen, 
sulphur,  chlorine,  phosphorus,  arsenic.  Color  and  appear- 
ance: like  platinum,  or  a  platinum-gold  alloy.  Structure: 
native,  grains  of  fibrous  appearance.  Consistence:  hard 
as  platinum.  Compounds:  palladium  (II)  and  palladic 
(IV).     'Alloys:  salmon-bronze. 

Use  in  dentistry;  in  amalgam  alloys.  (See  section 
223). 

288.  Platinum.— 

Symbol:  Pt.  Latin  Jiame:  Platinum.  Equivalence:  II, 
and  IV.  Specific  gravity:  21.50.  One  of  the  heaviest  sub- 
stances in  nature.  Atomic  weight:  197.  Revised  atomic 
iveight:  196.700;  (according  to  some,  194.8).  Electrical 
state:  +.  Fusing poifit:  above  3500°  in  oxyhydrogen  flame, 
or  coal-gas  and  oxygen  flame.  Length  of  bar,  etc.:  1.0009; 
(13th  rank,  least  expansible  of  the  13  metals).  Wt.  cubic 
ft.  in  lbs.:  1.344.  Tenacity:  15,  compared  with  lead;  (4th 
rank).  Malleability:  5;  (5th  rank).  Ductility:  3;  (3d 
rank).  Conducting  power  {heat):  8;  (8th  rank).  Con- 
ducting power  {electricity):    180   (silver   =    1,000):    (6th 


202  DENTAL   CHEMISTRY. 

rank).  Resista?ice  to  air,  etc.:  i;  (ist  rank).  Solubility. 
dissolves  slowly  in  aqua  regia.  Acted  on  by  fused  alka- 
line hydrates  at  red  heat.  Direct  cortibinationy.  sulphur, 
phosphorus,  arsenic,  silicon,  chlorine.  Absorbs  and  con- 
denses gases  when  in  finely  divided  state.  Color  and 
appearance',  white  with  tinge  of  blue,  brilliant  but  less 
than  silver.  Structure',  (native)  rounded  grains;  some- 
times octahedral  crystals.  Consistence:  hard  as  copper. 
Compounds:  platinous  (11),  and  platinic  (IV).  Alloys: 
with  most  metals.  Gold,  silver,  lead  form  easily  fusible 
alloys  with  it. 

Use  in  dentistry:  in  amalg-am  alloys,  for 
plates  of  continuous  gum  teeth,  for  pins  for 
fastening  porcelain  teeth  to  the  rubber  or  cellu- 
loid plate.  Metallic  platinum  does  not  amal- 
gamate with  mercury,  but  spongy  platinum 
unites  with  the  latter  when  triturated  with  it  in 
a  warm  mortar  or  in  contact  with  acetic  acid. 
(See,  however,  Rollins's  process,  following 
below).  In  finely  divided  state  it  is  used  as  a 
coloring  matter  for  artificial  teeth. 

Preparation  of  platinum  for  coloring  the  enamel  of 
artificial  teeth. — 

The  ordinary  platinum  sponge  is  too  coarse  to  produce 
the  best  results  without  much  grinding.  Rollins  proceeds 
as  follows:  Dissolve  twenty  grammes  of  platinum  in  aqua 
regia  and  evaporate  to  a  thick  syrup,  then  add  one  hun- 
dred grammes  of  caustic  potash  and  boil.  To  this  mixture 
add  fifty  grammes  of  grape  sugar  and  boil  ten  minutes. 
Wash  thoroughly  by  decantation  and  dry  the  residue, 
which  is  platinum  in  an  exceedingly  fine  state.  To  pre- 
pare what  is  to  be  called  "  Platinum  Color"  use  feldspar 
eight  grammes,  this  platinum  five  hundred  milligrammes. 


INORGANIC   CHEMISTRY.  203 

Mix  and  grind  five,  minutes  on  slab.     Use  this  mixture  to 
add  to  uncolored  spar  for  the  enamel. 

289.  Platinum  metals:  these  are  platinum, 
rhodium,  palladium,  ruthenium,  and  iridium. 

Occurrence:  the  chief  supply  of  platinum, 
which,  like  gold,  is  found  free,  is  derived  from 
the  Ural  Mountains.  The  Russian  platinum 
dig-g-ing-s  are  near  Bog'oslowsk,  Miask,  New- 
jansk,  and  Nischnei  Tagilsk.  It  is  also  found 
in  Brazil,  Peru,  Columbia,  California,  and 
Borneo.  The  Russian  platinum  is  always 
associated  with  other  metals:  analysis  showed 
in  one  specimen,  75.1  platinum,  i.i  palladium, 
3.5  rhodium,  2.6  iridium,  0.6  osmiridium,  2.3 
osmium,  0.4  gold,  i.o  copper,  and  8.1  iron.* 

Preparation:  the  platinum  is  dissolved  in 
fused  galena,  a  little  glass  is  introduced  to  melt 
over  the  surface,  and  a  quantity  of  litharge, 
equal  in  weight  to  the  galena,  is  gradually 
added.  Sulphurous  acid  gas,  from  the  lead 
sulphide  and  lead  oxide,  is  formed,  leaving 
metallic  lead  in  combination  with  the  platinum, 
free  from  osmium  and  iridium.  The  lead- 
platinum  combination  is  then  treated  in  a  citp- 
ellatioii  furnace,  that  is,  a  furnace  containing 
a  CMp,  made  of  bone  ash;  the  lead  removed  as 

*  The  annual  product  is  two  or  three  tons,  of  which  the  United 
States  furnish  about  200  ounces.  It  is  worth  about  $15  an  ounce, 
and  the  price  tends  to  rise  in  consequence  of  the  demand  for  it  for 
use  in  electric  licrhtinsr. 


204  DENTAL   CHEMISTRY. 

an  oxide,  leaving'  the  platinum  in  spongy 
state  on  the  cupel.  The  spongy  platinum  is 
refined  in  a  lime  furnace,  by  the  heat  of  an 
oxy-hydrogen,  or  coal  gas  and  oxygen  flame. 

290.  Compounds  of  platinum:  platinic  chloride,  Pt 
CU,  is  formed  when  metallic  platinum  is  dissolved  in 
aqua  regia.  It  is  a  reddish,  deliquescent  substance  readily 
soluble  in  water  and  in  alcohol. 

291.  Iridium.— 

Symbol:  Ir.  Latin  name:  Iridium.  Equivalence:  \\,\Y, 
VI.  Specific  gravity:  21. i.  Atojnic  weight:  192.7.  Re- 
vised atomic  weight:  192.651.  Electrical  state :  +.  Fusing 
point:  fusible  in  oxyhydrogen  blow-pipe;  more  refractory 
than  platinum.  Resistance  to  air:  unalterable  in  air.  Sol- 
ubility: not  soluble  in  aqua  regia  unless  alloyed  with  plat- 
inum. Direct  combinations:  sulphur,  chlorine,  iodine, 
oxygen.  Color  a7id  appearance :  white,  like  polished  steel. 
Consistence:  very  hard,  brittle.  Compounds:  iridic,  iridious, 
hypoiridious.  Alloys:  with  platinum.  Value  in  detitistry: 
for  alloy  with  platinum  in  manufacture  of  plates  and 
wire. 

292.  Silicon.— 

Symbol'.  Si.  Latin  name:  Silicium.  Equivalence:  II  and 
IV.  Specific  gravity:  2.49.  Atomic  weight  {appro x.):  28.2. 
Atomic  weight  {revised):  28.1950.  Electrical  state: — Solu- 
bility: in  melted  zinc,  etc.  Fusing  point:  above  melted 
iron.  Preparatio?i:  made  by  action  of  sodium  on  potas- 
sium fluo-silicate. 

Properties:  occurs  in  three  forms  somewhat  resemb- 
ling carbon.  Is  an  amorphous,  nut-brown  powder.  In 
combination,  as  silica,  SiOa,  found  in  sand,  rocks,  etc. 

293.  Compounds  of  silicon:  the  most  important  is 
silica,  SiOa.  Silica  occurs  in  nature  as  quartz  crystal  and 
in   sand.     Is  found   in  animal    tissues.     Compounds   are 


INORGANIC   CHEMISTRY.  205 

silicates.  Insoluble  in  water  or  acids,  infusible  except  by 
oxyhydrogen  flame,  sp.  gr.  2.66,  Percentage  composition, 
silicon,  48.04,  oxygen,  51.96.  Used  in  manufacture  of 
porcelain  teeth. 

IJse  in  dentistry:  dentists  use  silica  under 
the  name  of  silex  in  the  preparation  of  arti- 
ficial teeth.  For  dental  uses  it  is  prepared  by 
heating-  to  white  heat,  plunging  into  cold 
water,  and  grinding  to  a  fine  powder. 

294.  Titanium:  titanium  itself  is  not  used  in  dentistry^ 
and  the  only  compound  of  interest  is  the  dioxide,  titanic 
oxide,  TiOg,  which  occurs  native  in  several  different  forms, 
viz.,  as  the  minerals  rutile  and  anatase,  and  as  brookite. 

Rutile  is  the  most  abundant,  and  is  used, 
ground  up,  as  a  coloring  matter  for  artificial 
teeth.  If  ground  moderately  coarse  it  imparts 
a  yellow  of  redder  cast  than  when  ground  fine. 
It  is  used  for  the  yellow  color  of  the  body  of 
porcelain  teeth. 

295.    Carbon. — 

Symbol:  C.  Equivalence :  II  and  IV.  Atomic  weight 
{appro X. ) :  12.  Atomic  weight  {revised) :  11.9736.  Electri- 
cal state: —  .  Fusing  point :  infusible.  Properties:  affinity 
for  oxygen,  hydrogen,  sulphur.  Infusible,  non-volatile, 
unalterable  solid.     Absorbs  gases,  disinfectant. 

296.  Dental  nses- — In  the  form  of  charcoal,  coke,  and 
anthracite  coal,  carbon  is  used  in  the  dental  laboratory. 
In  the  form  of  animal  charcoal  and  of  wood  charcoal  it  is 
used  in  dental  medicine. 

Charcoal  is  prepared  on  a  large  scale  by  burning  wood 
in  heaps  with  limited  supply  of  air.  Carbo  lipii  is  the 
official  preparation. 


206  DENTAL    CHEMISTRY. 

Coke  is  the  substance  left  in  retorts  after  coal  has  been 
distilled  in  the  production  of  illuminating  gas. 

Anthracite  coal  is  the  result  of  the  slow  decay  of  vege- 
table matter.  It  often  contains  96  to  98  per  cent,  of 
carbon. 

Carbo  animalis  purificatus  consists  of  carbon  and  several 
salts  of  calcium,  notably  the  phosphate  and  the  carbon- 
ate. 

Charcoal,  and  especially  ajiimal  charcoal,  has  the  power 
of  absorbing  gases,  of  destroying  noxious  odors,  and  of 
filtering  coloring  matters  from  solutions  of  organic  sub- 
stances. One  volume  of  wood  charcoal  at  2I2°F  will 
absorb  90  volumes  of  ammonia  gas,  55  volumes  of  sulphur- 
etted hydrogen,  and  9  volumes  of  oxygen.  It  is  admin- 
istered internally  to  counteract  the  effect  of  poisons,  as, 
for  example,  strychnine,  but  should  be  removed  by  the 
stomach  pump. 

297.  Illuminating  gas  is  made  by  subjecting  bitumi- 
nous coal  to  the  action  of  dry  heat  in  retorts.  The  coal 
is  heated  to  bright  redness,  and  the  products  given  off 
from  it  are  passed  through  a  series  of  upright  tubes,  in 
form  of  an  inverted  U,  called  condensers,  where  the  tar, 
steam,  and  ammonia  are  condensed.  The  gas  is  then 
passed  through  a  series  of  large  boxes  called  purifiers, 
in  which  it  is  purified  by  coming  into  contact  with  various 
substances  as  fresh  slaked  lime  or  a  mixture  of  sawdust 
and  iron  oxide,  and  then  it  goes  to  a  large  tub-shaped 
vessel  called  the  gasometer  to  be  stored  until  needed. 

It  is  a  mixture  essentially  of  hydrogen  and  marsh-gas 
mixed  with  variable  proportions  of  olefiant  gas,  acetylene, 
the  oxides  of  carbon,  etc.,  etc.  [Much  of  the  illuminating 
gas  now  used  is  the  so-called  "  water-gas,"  which  con- 
tains usually  a  considerable  amount  of  carbon  monoxide, 
and  is  made  by  decomposing  steam  and  then  carburet" 
ting  the  gases  formed]. 


INORGANIC   CHEMISTRY.  207 

298.  Compounds  of  carbon.— 

Carbon  forms  two  compounds  with  oxygen,  namely, 
carbon  vionoxide  and  dioxide.  Carbon  monoxide,  CO,  is 
formed  when  carbon  is  burned  in  deficient  supply  of  air. 
Molecular  weight,  28;  density,  14;  sp.  gr.,  0.9678.  Is  a 
gas.  Colorless,  insipid,  very  poisonous,  insoluble,  com- 
bustible. 

Called  also  "carbonic  oxide  gas." 

Carbon  dioxide,  CO2,  is  a  product  of  combustions  and  of 
fermentation.  Made  by  pouring  an  acid  on  a  carbonate, 
as  sulphuric  acid  on  marble  or  limestone.  Molecular 
weight,  44;  density,  22;  sp.gr.,  1.529.  Colorless,  odorless 
gas,  present  in  air,  water,  breath,  heavier  than  air.  Nar- 
cotic. Slightly  acid  taste.  Very  soluble  in  water.  Com- 
pounds are  carbonates. 

Carbonic  Acid  gas,  known  to  chemists  as  carbonic 
dioxide,  or  carbon  dioxide,  is  a  constituent  of  the  breath, 
is  found  in  small  quantities  in  the  atmosphere,  and  is  a 
product  of  fermentation.  It  is  not  a  true  acid,  as  defined 
in  this  book,  but  an  anhydride,  carbonic  anhydride,  COj,. 
The  hydrated  acid  is  not  found,  but  its  salts  exist,  as,  for 
example,  the  various  carbonates,  like  sodium  carbonate, 
Na^COa. 

299.  Carbon  Disulpliide.— 

Synonyms:  carbon  bisulphide,  carbon  bisulphuret  or 
bisulphuret  of  carbon.  Official  name,  Carbonei  Bisul- 
phidum. 

Theoretical  constitution:  CSo,  one  atom  of  carbon  and 
two  of  sulphur.     Molecular  weight,  76. 

Preparation:  made  by  passing  fumes  of  sulphur  over 
red  hot  charcoal. 

Properties:  mobile,  colorless  liquid  of  disgusting  odor 
except  when  pure.  Very  volatile.  Dissolves  iodine,  sul- 
phur, phosphorus,  oils,  fats,  caoutchouc,  etc.  Sometimes 
used  as  local  anaesthetic. 


20S  DENTAL   CHEMISTRY. 

Use  in  dentistry:  to  dissolve  caoutchouc. 

Pentads  and  Hexads. 

300.  None  of  the  pentads  are  used  in  dentistry  except 
those  classified  as  triads,  when  varying  in  equivalence. 
The  following  list  shows  hexads  of  importance: 

Table  24.    Important  Hexads. 

Manganese.  ^     Hexads 
Iron.  !     positive 

Nickel.  r        to 

Cobalt.  J  hydrogen. 

]     Hexad 
Chromium.    V  negative  to 

)  hydrogen. 

301.  Manganese. — 

Symbol:  Mn.  Latin  ?iame:  Manganesium.  Equivalence : 
II,  IV,  VI;  also  a  pseudo-triad.  Specific  gravity :  8.01  to  8.03. 
Atomic  weight  {approx.):  53.9.  Atomic  weight  {revised): 
53.9060.  Electrical  state:  +.  Properties:  grayish  white 
metal  of  but  little  lustre,  hard,  brittle,  and  nearly  as  re- 
fractory as  platinum. 

302.  Compounds  of  manganese.— 

The  only  important  compound  for  dental  uses  is  the 
dioxide,  MnOg,  which,  in  minute  quantity,  imparts  a  pur- 
ple color  to  the  frit,  probably  due  to  formation  of  an  oxy- 
silicate.  A  silicate  is  also  used  in  enamels;  it  is  a  yellow 
amorphous  powder  turning  brown  on  exposure  to  air  and 
soluble  in  dilute  acids. 

Manganese  dioxide  occurs  in  nature  as  the 
mineral  f^yrolusite.  It  is  a  heavy,  black,  crys- 
talline mineral  insoluble  in  water.  When 
heated  to  redness  it  liberates  oxygen. 


INORGANIC   CHEMISTRY.  209 

303.    Iron. 

Symbol:  Fe.  Latin  7iame :  Ferrum.  Equivalence :  II, 
IV,*  VI.  Specific  gravity :  7.79107.84.  Atomic  weight:  ^^d. 
Revised  atomic  weight :  55.9130.  Electrical  state :  +•  Fusing 
poi)it:  3500°F  (wrought  iron).  Ordinary,  2900''F.  Length 
of  bar:  1.0012  (loth  rank).  Weight  of  cubic  fi)ot  in  lbs.: 
489.4.  Tensile  strength:  29.0  (maximum).  Tenacity:  27 J^, 
steel,  42,  (ist  rank).  Malleability:  8;  (8th  rank).  Duc- 
tility: 4;  (4th  rank).  Conducting  power  {heat):  6;  (6th 
rank).  Conducting  power  {electricity) :  \6^;  (silver  ==  lOOO); 
(7th  rank).  Resistance  to  atr:  rnsis'inraoistsdr.  Solubility: 
soluble  in  hydrochloric  and  sulphuric  acids;  in  dilute 
nitric.  Direct  combinations:  chlorine,  bromine,  iodine, 
sulphur,  and  members  of  the  phosphorus  group  except 
nitrogen.  Color  and  appearance :  ^Q.^Qndi  on  vzx'x&X-y .  Pure 
iron  is  white.  Structure :  white  cast  iron,  crystalline;  gray 
iron,  granular;  wrought  iron,  fibrous;  crystals  probably 
cubical.  Consistefice :  pure  iron  is  soft  and  tough.  Com- 
pounds: ferric  (Fe.^)^',  ferrous  (Fe"),  and  ferroso-ferric,  Fe" 
(Fca)^'.  Alloys:  Aich's  metal,  arguzoid.  German  silver 
plate,  sterro-metal. 

Use  in  dentistry:  as  steel,  and  in  many  ways. 

Occurrence:  the  iron  ores  are  very  numer- 
ous and  widely  distributed;  those  used  in  the 
manufacture  of  iron  are  haematite  (FeaOa), 
mag-netite  (FeaO*),  hmonite  (a  hydrate),  and 
siderite  (FeCOg). 

Preparation:  the  general  process  is  to  reduce 
with  carbon,  metallic  iron  and  the  oxides  of 
carbon  being-  formed.  Sometimes  the  ore  is 
first  roasted  to  g"et  rid  of  sulphur,  carbonic 

*  Iron  as  a  pseudo-triad  in  ferric  compounds  is  really  quadriva- 
lent. 


210  DENTAL   CHEMISTRY. 

acid,  water,  etc.  The  ore,  containing  iron  ox- 
ide, is  then  reduced,  /.  e.,  deprived  of  its  oxy- 
gen, in  a  blast  furnace,  which  is  filled  at  the 
top  with  alternate  layers  of  coal,  broken  ore, 
and  fluxes,  such  as  limestone  or  silicates.  Iron 
obtained  by  this  method  is  known  as  cast- 
iron,  and  contains  more  or  less  carbon  and 
slag-,  when  drawn  off  into  moulds  to  form  pig- 
iron.  Wrought-iron  is  made  by  subjecting; 
pig-iron  to  the  puddling  process,  during  which 
the  molten  metal  is  thoroughly  stirred  in  rever- 
berating' furnaces,  where  there  is  a  free  supply 
of  air,  so  that  the  carbon  of  the  pig-iron  is 
burned  and  other  impurities  oxidized. 

304.  Steel  is  now  made  by  the  Bessemer 
process,  by  blowing-  air  under  great  pressure 
into  molten  cast-iron,  consuming  the  carbon; 
iron  rich  in  carbon  and  manganese,  termed 
spiegel-eisen,  is  then  added  to  give  the  proper 
amount  of  carbon. 

Malleable  iron  is  steel  which  has  undergone 
further  treatment  by  heat  and  atmospheric  air. 

305.  Dental  uses  of  iron:  chiefly  in  tools; 
iron  is  by  far  the  strongest  and  yet  one  of  the 
lightest  of  the  metals;  steel  is  the  strongest 
and  one  of  the  hardest  and  most  elastic  of  all 
materials;  malleable  iron  possesses  great 
strength  and  toughness,  but  is  soft  enough  to 
be  turned,  bored,  and  punched,  and,  when 
heated,  is  easily  wrought  and  without  crack- 


INORGANIC   CHEMISTRY.  211 

ing^.  Wrought-iron,  at  bright  red  heat,  can  be 
welded,  that  is,  joined  to  another  piece  of 
metal,  without  the  use  of  solder.  Wrought- 
iron  has  the  property  of  acquiring  with  great 
rapidity  the  properties  of  a  magnet  and  of 
parting  with  them  rapidly,  hence  is  well 
adapted  for  use  in  the  construction  of  electro- 
magnetic and  magneto-electric  apparatus. 
Cast-iron  is  easily  melted,  and  can  be  made 
into  castings,  which  may  be  readily  filed  or 
turned,  or  made  so  hard  that  no  tool  can  affect 
them. 

When  cold,  iron  is  the  least  malleable  of 
metals  in  common  use,  but  when  heated,  its 
ductility  is  such  that  it  can  be  rolled  into  the 
thinnest  sheets  and  drawn  into  the  finest  wire, 
which,  when  lUh  inch  in  diameter,  will  sustain  ^ 
a  weight  of  700  pounds.  With  exception  of 
platinum,  iron  is  the  least  fusible  of  the  useful 
metals. 

306.  Compounds  of  Iron:  compounds  of  Iron  are 
chiefly  of  two  kinds,  fernV  and  ierrous: 

Ferric  compounds:  iron  as  a  pseudo-triad.  Ferric 
chloride,  Fe2Cl6,  per-chloride,  sesquichloride,  chloride  of 
iron,  Ferri  Chloridum;  orange-yellow,  deliquescent,  solu- 
ble. Liquor ferri chloridi,  U.S.  v.,  con\.dar\s,  37.8  per  cent, 
of  the  anhydrous.  "  Tincture  of  Iron"  is  one  part  of  the 
Liquor  X.O  about  two  of  alcohol  (Tinctura  Ferri  Chloridi, 
U.  S.  P.);  hemostatic,  strong  chalybeate,  styptic  taste, 
acid  reaction,  stains  teeth  and  acts  on  them.  Ferric  Hy- 
drate, Fe2(HO)6,  hydrated  oxide,  hydrated  peroxide,  per- 
oxide, sesquioxide,  red  oxide.    Precipitate  ferric  sulphate 


212  DENTAL   CHEMISTRY. 

or  ferric  chloride  by  ammonia  or  by  sodium  hydrate. 
Reddish-brown  powder  used  as  antidote  to  arsenic;  must 
be  freshly  made.  Hydrated  oxide  of  iron  with  magnesia,  U. 
S.  P.,  made  by  adding  magnesia  to  a  solution  of  ferric 
sulphate.  Ferric  Sulphate,  FQ^i'^Oi)^,  in  solution  forming 
"  solution  of  tersulphate  of  iron,"  U.  S.  P.,  color  reddish- 
brown.  Ferric  Substdphate  (doubtful  composition)  FCiO 
(804)5,  called  "Monsel's  solution,"  ruby-red;  valuable  as  a 
hemostatic,  may  be  taken  internally.  Dialyzed  Iron,  aque- 
ous solution  of  about  5  per  cent,  of  ferric  hydrate  with 
some  ferric  chloride.  Ammonia  is  used  in  making  it,  and 
the  ammonium  chloride  formed  passed  through  a  dialyzer. 
Ferrous  compounds:  iron  as  a  dyad.  Ferrous  salts 
are  usually  green,  and  alter  in  the  air  to  -ic  salts.  Ferrous 
chloride,  FeCl2,  protochloride;  ferrous  iodide,  Felg,  protio- 
dide,  green,  volatile,  deliquescent,  soluble.  Ferrous  sul- 
phide, FeS,  protosulphide,  sulphuret  of  iron,  is  used  to 
make  H2S  (sulphuretted  hydrogen).  Ferrous  sulphate, 
FeSOi,  green  vitriol,  copperas;  dissolve  iron  in  1%  parts 
H2SO4  diluted  with  4  parts  water:  efflorescent,  bluish- 
green  crystals,  acrid,  styptic  taste,  soluble  in  water,  in- 
soluble in  alcohol,  astringent,  irritant,  disinfectant. 

307.  Dental  uses  of  compounds  of  iron: 
ferric  chloride  is  used  externally,  to  arrest  alve- 
olar haemorrhage,  either  in  form  of  the  deli- 
quesced crystals  or  in  solution.  It  is  also  ap- 
plied to  fung"ous  tumors.  It  is  given  internal- 
ly. Monsel's  powder  and  solution  are  used  to 
arrest  haemorrhages  following  extraction  of 
teeth,  etc.,  etc. 

308.  Nickel.*— 

*Nickel  is  one  of  the  toughest  of  all  metals,  and  is  now  used  in 
manufacture  of  crucibles  which  to  some  extent  are  taking  the  place 
of  platinum  crucibles,  as  they  cost  only  about  one-tenth  as  much. 


INORGANIC   CHEMISTRY,  213 

Symbol:  Ni.  Latin  name :  Niccolum.  Equivalence :  II, 
IV,  (Ni.)  .  Specific  gravity :  8.60  to  8.82.  Atomic  weight : 
58.  Revised  atomic  weight:  57.928.  Electrical  state:  +. 
Fusifig point :  less  than  iron.  Weight  of  cubic  foot  in  lbs: 
541.2.  Tensile  strength:  same  as  iron.  Tenacity:  like  iron, 
very  great.  Malleability,  Ductility:  very  ductile  and 
malleable.  Conducting  power  {heat) :  about  the  same  as 
iron.  Conducting  poiver  {electricity):  131;  (8th  rank). 
Resistance  to  air:  rusts  less  readily  than  iron;  magnetic. 
Solubility:  soluble  in  dilute  mineral  acids,  especially 
nitric.  Direct  combinations:  with  chlorine,  cyanogen, 
oxygen,  sulphur,  arsenic.  Color  and  appearance:  silver- 
white,  with  a  slight  yellowish  tinge  and  very  lus- 
trous. Consistence:  hard.  Compounds:  mostly  nickelous. 
Alloys',  arguzoid,  electrum,  German  silver,  tutenag. 

309.    Cobalt. — 

Symbol:  Co.  Latin  name:  Cobaltum.  Equivalence:  II, 
IV,  (Co2)^^  Specific  gravity:  8.49  to  8.9.  Atomic  weight: 
58.9.  Revised  atomic  weight:  58.8870.  Electrical  state:  +. 
Fusing  point:  less  than  that  of  iron.  Weight  of  cubic  foot  in 
lbs.:  558.7.  Tensile  strength:  like  iron.  Tenacity:  like  iron. 
Malleability:  like  iron.  Ductility:  like  iron.  Resistance 
to  air:  like  nickel.  Solubility:  like  nickel.  Direct  com- 
binations: chlorine,  oxygen,  sulphur.  Color  and  appear- 
ance: reddish-white;  magnetic.  Structure:  has  granular 
fracture.  Consistence:  hard.  Compounds:  cobaltous,  cobal- 
tic,  and  cobaltous-cobaltic  like  ferroso-ferric. 

Compounds  of  Cobalt.—* 

Impure  protoxide  of  cobalt  serves  as  a  basis 
for  the  preparation  of  the  colors  of  cobalt, 
among;  which  are  various  blues.  Oxide  of 
cobalt  is  sometimes  used  for  the  blue  color  of 
points  of  porcelain  teeth. 

*The  term  "  cobalt  "  is  sometimes  applied  to  metallic  arsenic. 


214  DENTAL   CHEMISTRY. 

310.  Chromium. — 

Symbol:  Cr.  Latin  name:  Chromium.  Equivalence:  II, 
IV,  VI,  and  pseudo-triad.  Specific  gravity:  7.01.  Atomic 
weight  {approx.):  52.  Atomic  weight  {^revised):  52,009, 
Electrical  state:  — . 

311.  Compounds  of  Chromium,  Chromic  Anhy- 
dride.— 

Synonyms:  chromic  trioxide,  chromic  oxide,  chromic 
acid.     Official  name,  Acidum  Chromicum. 

Theoretical  constitution:  chromic  "  acid  "  so-called  is 
not  an  acid  but  an  oxide,  CrOs,  composed  of  one  atom  of 
chromium  to  three  of  oxygen;  by  weight,  52  parts  of 
chromium  to  48  of  oxygen.     Molecular  weight,  100. 

Preparation:  chromic  anhydride  separates  in  crystals 
from  a  mixture  of  potassium  dichromate  and  sulphuric 
acid : 

K,Cr20,    -f    2H2SO4   =    2Cr03  -f    2KHSO4  +   HgO 

Potassium  Sulphuric  Chromic  Acid  potassium 

dichromate.  acid.  anhydride.  sulphate. 

Properties:  fine  red,  very  deliquescent,*  needle-shaped 
cr^'stals,  which  have  strongly  corrosive  action  on  organic 
matter,  and  decompose  certain  substances  with  explosive 
violence,  as  alcohol,  sugar,  or  glycerine.  It  forms  dichro- 
mates  with  oxides  of  the  alkali  metals,  as  potassium 
dichromate  with  potassium  o.xide: 

K2O     +     2Cr03     =     K^Cr^O;. 

Potassium  Chromic  Potassium 

oxide.  oxide.  dichromate. 

The  crystals  are  readily  soluble  in  watfer,  forming  an 
orange  yellow  solution  of  strongly  acid  properties.  Alco- 
hol is  inflamed  by  the  crystals. 

Dental  uses,  etc.:  used  in  dentistry  locally,  for  removal 
of  tumors,  morbid  growths,  etc.,  etc.  If  combined  with 
glycerine,  care  must  be  taken  not  to  mix  too  rapidly,  but 

^Absolutely  pu>-e  chromic  acid,  wholly  free  from  sulphuric  acid, 
should  not  deliquesce  when  used  as  a  caustic. 


INORGANIC   CHEMISTRY.  215 

drop  by  drop  to  avoid  explosion.      It   penetrates   tissues 
deeply. 

Toxicology:  chromic  acid  is  a  poison,  and  a  violently 
corrosive  agent.  Poisoning  by  it  should  be  treated 
promptly  and  with  vigor  as  in  case  of  poisoning  by  sul- 
phuric acid.  Cause  the  patient  to  drink  at  once  water 
containing  300  to  400  grains  of  magnesia,  or  else  half  an 
ounce  of  soap  which  has  been  dissolved  in  two  quarts  of 
hot  water  and  cooled,  or  water  with  which  wood  ashes 
have  been  mixed,  or  a  solution  of  sodium  bicarbonate  (150 
grains  in  a  pint  of  water).  If  nothing  else  is  at  hand,  give 
milk  or  the  whites  of  four  eggs  in  a  quart  of  water.  Burns 
from  it  should  be  treated  as  in  case  of  hydrochloric  acid, 
and  as  promptly  as  possible. 

Chromic  oxide  of  formula  CraOa,  better 
known  as  the  sesquioxide,  is  a  green  powder 
insoluble  in  water  and  in  acids.  It  is  obtained 
by  heating  potassium  dichromate  with  sulphur. 
It  is  used  as  a  coloring"  matter  for  porcelain 
teeth  to  modify  or  tone  the  bright  yellow  of  the 
oxide  of  titanium  in  the  darker  shades. 


216  DENTAL   CHEMISTRY. 


CHAPTER  IV. 

CARBON    COMPOUNDS   0«    ORGANIC   CHEMISTRY. 

312.    Theory.— 

1.  Organic  Chemistry  is  the  chemistry  of 
carbon  compounds. 

2.  The  elements  found  in  org^anic  com- 
pounds are,  besides  carbon,  chiefly  hydrogen, 
oxygen,  and  nitrogen,  sometimes  sulphur  and 
phosphorus. 

3.  The  general  properties  of  organic  com- 
pounds are  as  follows:  combustible  (except 
CO2  and  its  salts) ;  solids  usually  when  carbon 
atoms  predominate  in  their  molecule;  liquids 
or  gaseous  when  hydrogen  predominates; 
easily  volatilized  gases  or  liquids  when  a  small 
number  of  atoms  in  the  molecule;  liquids  of 
high  boiling  points  or  solids  when  the  number 
of  atoms  in  the  molecule  is  large. 

4.  Quantitative  analysis  more  important  than  qualita- 
tive to  establish  identity  of  organic  compounds.  If  the 
elements  of  an  organic  substance  are   determined,   the 


ORGANIC   CHEMISTRY.  217 

analysis  is  called  ultimate  or  elementary;  if  different  organic 
substances  when  mixed  together  are  separated,  the 
analysis  is  called  proximate. 

5.  The  presence  of  carbon  in  a  combustible  form  will 
prove  a  compound  to  be  organic,  hence,  if  a  substance 
burns  with  generation  of  carbon  dioxide  (shown  by  pass- 
ing the  gas  through  lime-water)  the  organic  nature  of 
this  substance  is  established.  The  presence  of  hydrogen 
may  be  shown  by  allowing  the  gaseous  products  of  com- 
bustion to  pass  through  a  cool  glass  tube,  when  drops  of 
water  will  be  deposited.  To  show  presence  of  nitrogen, 
heat  with  a  mixture  of  two  parts  calcium  hydrate  to  one 
part  sodium  hydrate;  the  nitrogen  is  converted  into  am- 
monia, recognized  by  its  odor  and  action  on  paper 
moistened  with  copper  sulphate  solution. 

6.  A  c\).Q.m\c-d\  formula  is  called  empirical  when  it  gives 
the  simplest  expression  of  the  composition  of  a  sub- 
stance; this  formula,  however,  does  not  necessarily  denote 
the  actual  number  of  atoms  in  the  molecule,  which  may 
be  two  or  three  times  the  number  given  in  the  empirical 
formula;  thus,  the  empirical  formula  of  acetic  acid  is 
CH2O,  but  the  actual  molecular  formula  contains  twice 
the  number  of  atoms  or  C2H4O2.  Besides  empirical  and 
molecular  formulae,  others  called  rational,  constitutional, 
structural,  or  graphic  are  used.  The  molecular  formula  of 
acetic  acid  is  CgHjOa,  but  the  formula  HC2H3O2  shows 
that  acetic  acid,  like  nitric  acid,  HNO3,  is  monobasic, 
containing  one  atom  of  hydrogen,  which  can  be  replaced 
by  an  atom  of  a  metal;  hence  HCgHsOa  is  called  a  consti- 
tutional formula. 

7.  Radicals  or  residues.  These  are  expressions  for  un- 
saturated groups  of  atoms  known  to  enter  as  a  whole  into 
different  compounds,  but  having  no  separate  existence. 
Water,  HjO,  is  a  saturated  compound,  that  is  the  one  atom 
of  oxygen — which  is  a  dyad,  and  may  be  said  therefore 


218  DENTAL   CHEMISTRY. 

to  have  two  points  of  attraction — combines  with  two  of 
hydrogen  and  therefore  has  both  its  points  of  attraction 
satisfied.  If  now  one  atom  of  H  be  taken  from  H2O, 
there  is  left  the  group  of  atoms  HO,  which  is  called  a 
radical,  as  it  consists  of  an  atom  of  oxygen,  in  which  but 
one  point  of  attraction  is  actually  saturated,  the  second 
one  not  being  provided  for;  moreover,  this  group  HO  oc- 
curs in  many  compounds — as,  for  example,  in  the 
hydrates,  as  potassium  hydrate,  KHO,  etc.  The  equival- 
ence of  radicals  depends  upon  the  number  of  points  of  at- 
traction unprovided  for:  carbon  requires  four  atoms  of 
hydrogen  to  provide  for  its  points  of  attraction;  therefore 
CH3  would  be  a  monad,  CH2  a  dyad,  CH  a  triad.  (See 
Chapter  H). 

Radicals  are  electro-positive  and  electro- 
negative. The  most  important  positive  radi- 
cals are  ammonium  NH4,  the  ethyl  series  of 
radicals  (such  as  methyl  CH3,  ethyl  CH4,  etc.) 
and  also  of  other  series,  phenyl,  glyceryl,  etc. 

The  most  important  negative  radicals  are 
acid  radicals,  as  C2H3O2,  that  of  all  acetates, 
C2O4  that  of  all  oxalates,  etc.  HO  the  radical 
of  hydrates  and  CN  of  cy3.nides  are  negative 
also. 

8.  Chains:  the  expression  chain  denotes  a  series  of 
atoms,  held  together  in  such  a  manner  that  affinities  are 
left  unsaturated.  The  atoms  of  the  series  must  have  a 
greater  equivalence  than  one,  i.  e.,  must  be  dyad,  etc.  The 
existence  of  such  an  enormous  number  of  carbon  com- 
pounds is  greatly  due  to  the  property  of  carbon  to  form 
these  chains.     Carbon  is  a  tetrad,  hence  two  atoms  would 

form  a  chain  as  follows: — C — C — ;  each  atom   has  four 


ORGANIC   CHEMISTRY.  219 

bonds,  one  of  which  unites  with  one  of  the  other,  leaving 
in  this  particular  chain  six  free  affinities.     Three  atoms  of 


i-; 


carbon   would   be   — C — C — C — ;  four,  — C — C — C — C — , 

111  I       I       I       I 

etc.,  etc.  The  ftee  affinities  may  be  saturated  with  vari- 
ous atoms  or  radicals,  hence  the  almost  unlimited  number 
of  possible  combinations.  Atoms  are  not  always  united 
by  one  affinity.  When  they  are  united  by  two,  the  ex- 
pression for  two  atoms  of  carbon  would  be^C  =  0  ('■> 

if  by  three,  — C^C — .  In  the  so-called  closed  chain  of  Ce 
we  have  the  atoms  united  partially  by  double  and  partial- 
ly by  single  union: 

I 

c  c 


i 


II 
c 


/Xc 


Benzine,  CeHj,  would  then  be  represented  as  follows: 

H 


I         II 

c  c 

I 
H 

It  is  easy  to  see  from  these  two  diagrams  the  origin  of  the 
term  skeleton,  which  is  sometimes  used  instead  of  chain. 

g.     Homologous  series.       Any   series   of    organic   com- 
pounds, the  members  of  which  preceding  or  following 


220  DENTAL    CHEMISTRY. 

each  other  differ  by  CH2,  is  called  a  homologous  series  * 

10.     Types.     Most  substances  may  be  classified  under 

the  five  following  types; 


I. 

11. 

III. 

IV. 

Hydrogen. 

Water. 

Ammonia. 

Methane. 
H 

/H 

1    /" 

H— H 

H— 0— H 

N— H 

C^ 

\H 

1  XH 
H 

V. 

Phosphoric  chloride. 

CI 

l/ci 

P— CI 

• 

Ixci 

CI 

Almost  any  compound  may  be  classed  in  one  of  these 
types  by  replacing  the  constituents  of  these  types  by  other 
elements  or  radicals  of  the  same  equivalence. 

11.  Substitution.  Replacement  of  an  atom  or  group  of 
atoms  by  other  atoms  or  groups:  CgHg  +  HNO3  = 
CfiHsNOz  +  H2O.  Here  for  one  atom  of  hydrogen  in 
benzine  (CeHj)  has  been  substituted  the  group  NO;;.  (See 
Chap.  II). 

12.  Derivatives.  Chloroform,  CHCI3,  is  a  derivative  of 
marsh  gas,  CH^,  because  it  may  be  obtained  from  the  lat- 
ter by  replacement  of  three  atoms  of  hydrogen  by  three 
of  chlorine.  The  term  is  applied  to  bodies  derived  from 
others,  by  some  kind  of  decomposition,  generally  by 
substitution.     (See  Chap.  II). 

13.  Isomerism.  Two  or  more  substances  having  the 
same  elements  in  the  same  proportions  by  weight,  or  hav- 
ing the   same   percentage   composition,    and   yet    being 

When  the  carbon  remains  the  same  but  the  hydrogen  differs  by 
Ha,  the  series  is  said  to  be  isoiogous. 


ORGANIC   CHEMISTRY.  221 

different  bodies  with  different  properties,  are  called 
isomeric  bodies.  When  two  or  more  substances  have  the 
same  molecular  formulas  they  are  said  to  be  metameric 
with  one  another;  thus  CNgH^O  is  either  urea  or  ammon- 
ium cyanate;  hence,  urea  is  said  to  be  metameric  with 
ammonium  cyanate.  Sometimes  structural  formulae  will 
serve  to  distinguish  two  substances  metameric  with  each 
other.  When  a  substance  contains  some  multiple  of  the 
number  of  each  of  the  atoms  contained  in  the  molecule  of 
the  other,  it  is  said  to  be  polymeric  with  it;  thus  acetic 
acid  C2H4O2,  is  polymeric  with  grape-sugar,  CgHiaOj. 
(See  Chap.  II). 

14.  Decomposition.  Organic  bodies  decompose  readily 
under  the  influence  of  heat  or  chemical  agents.  Heat  will 
volatilize  some  organic  bodies  without  decomposition; 
whilst  others  are  decomposed  by  heat  with  generation  of 
volatile  products.  Dry  or  destructive  distillation  is  the 
term  applied  to  the  process  of  heating  non-volatile  organic 
substances  in  such  a  way  that  the  oxygen  in  the  air  has 
no  access  and  to  such  an  extent  that  decomposition  takes 
place.     (See  Chap.  II). 

15.  Combustion  and  decay.  In  common  combustion, 
provided  an  excess  of  atmospheric  air  be  present,  the  car- 
bon of  an  organic  substance  is  converted  into  carbon 
dioxide,  the  hydrogen  into  water,  sulphur  and  phosphorus 
into  sulphuric  and  phosphoric  acids,  and  the  nitrogen 
set  free.  In  decay,  which  is  slow  oxidation,  the  com- 
pounds mentioned  above  are  finally  produced,  but  many 
intermediate  products  are  also  generated.  Alcohol  when 
burned  forms  carbon  dioxide  and  water;  exposed  to  the 
air,  it  undergoes  slow  oxidation,  forming  aldehyde  first, 
then  acetic  acid. 

16.  Fermentation  and  putrefaction.  An  organic  substance 
under  favorable  temperature  and  during  the  presence  of 
moisture  and  of  a  substance  termed  a  ferment,  undergoes 


222  DENTAL   CHEMISTRY. 

a  peculiar  kind  of  decomposition,  during  which  its  mole- 
cule is  split  up  into  two  or  more  molecules  of  less  compli- 
cated composition. 

1 7.  Difference  between  fennentation  and  putrefaction.  ( See 
Ferments,  section  476). 

18.  Action  of  various  agents  on  organic  matter.  Chlorine 
and  bromine  usually  remove  or  replace  the  hydrogen  of 
an  organic  substance.  Sometimes  they  combine  directly 
with  it,  and  sometimes,  in  presence  of  water,  act  as  oxi- 
dizing agents  by  combining  with  the  hydrogen  of  the 
water  and  liberating  oxygen.  Nitric  acid  either  forms 
(i)  salts  with  organic  matter,  (ii)  oxidizes  it,  or  (iii)  sub- 
stitutes N08  (nitryl)  for  hydrogen.  In  the  latter  case 
the  additional  quantity  of  oxygen  added  renders  the  com- 
pounds highly  combustible  or  even  explosive.  Substances 
having  a  great  affinity  for  water,  as,  for  example,  sulphuric 
acid,  act  on  many  organic  substances  by  removing  hydro- 
gen and  oxygen,  leaving  dark  or  black  compounds  con- 
sisting mainly  of  carbon.  Alkalies  may  combine  directly, 
form  salts,  form  soaps,  oxidize,  or  evolve  ammonia  from 
nitrogenous  compounds.  Reducing  agents,  especially 
nascent  hydrogen,  either  combine  directly,  remove  oxy- 
gen, or  replace  oxygen. 

313.  The  following  synopsis  will  give  the  student  a 
general  idea  of  the  constitution  and  derivation  of  the 
various  classes  of  organic  compounds. 

Class  1.  Hydrocarbons.  Compounds  of  hydrogen  and 
carbon  only. 

Paraffin  or  methane  series',  saturated,  of  general  formula 
Cn  H2n+2.  names  end  in — ane;  examples:  methane  CH4, 
ethane  CjHe,  propane,  butane,  pentane,  hexane,  heptane, 
octane,  etc.,  etc.,  occur  in  nature  as  in  petroleum,  natural 
gas,  ozokerite.     First  four  of  series  are   colorless  gases, 


Organic  chemistry.  223 

higher  members  solids.  They  cannot  combine  directly 
with  elements,  being  saturated.  Attacked  by  CI,  and  Br 
in  sunlight  with  formation  of  substitution  products. 

Olefiiie  or  ethylene  series  :~-\}n%2i\.\xx2X&di.  General  formula, 
CnHan,  names  end  in — ene,  ethylene  C2H4,  amylene  C5H10. 
May  be  prepared  by  action  of  dehydrating  agents, 
as  H2SO4,  on  alcohols.  Burn  with  luminous,  smoky  flame. 
Are  gases,  liquids,  solids  in  order  of  series.  Combine  dir- 
ectly with  elements,  and  are  readily  oxidized. 

Acetylene  series : — Unsaturated. General  formula,  Cn  ^2^—1. 
Acetylene,  C2H2,  allylene,  C3H4.  May  be  prepared 
by  treating  monohalogen  substitution  products  of  olefines 
with  alcoholic  potash.  (Acetylene  occurs  in  coal-gas). 
Are  gases  or  volatile  liquids  of  peculiar  odor.  Burn  with 
luminous,  very  smoky  flame.     Combine  directly. 

Class  II.  Monohydric  Alcohols.  Hydroxy-derivatives 
of  paraffins.  General  formula  CnHan+i-OH.  Names  end  in 
— yl,  as  methyl  alcohol  CH3.OH,  ethyl  alcohol  C2H5.OH 
etc.,  the  name  in  — yl,  however,  being  that  of  a  radical  (see 
section  359).*  Are  primary,  secondary,  or  tertiary:  primary 
contain  the  group  — CHj.OH,  secondary  >CH.OH,  and 
tertiary  — C.OH.  Examples:  propyl  alcohol  CH3  .CHj. 
CH2.OH,  isopropyl  alcohol  CH3.CH.(OH).  CH3,  tertiary 
butyl  alcohol  CHjX. 

CH3— ^^C(OH) 
CH3/ 

Neutral,  colorless  liquids  of  characteristic  odor  and 
burning  taste.  A  few  higher  members  of  series  are  solids. 
React  more  readily  than  paraffins  owing  to  presence  of 
hydroxyl  group.  Oxidizing  agents  convert  primary 
alcohols  into  aldehydes  and  then  into  fatty  acids,  which 
see  below. 

Class  III.     Ethers.     Contain  an  oxygen  atom  united 

*The  student  should  commit  to  memory  the  radicals  in  table  25,  especially  the  first 
five. 


224  DENTAL    CHEMISTRY. 

to  two  hydrocarbon  groups  as  methyl  ether  CH3.O.CH3, 
corresponding  to  K.O.K,  just  as  methyl  alcohol  CH3.OH 
corresponds  to  K.OH.  May  be  prepared  by  heating 
alcohols  with  H2SO4.  Are  all  liquids  except  methyl 
ether,  a  gas,  and  are  mobile.volatile,  inflammable.  Arede-  ■ 
composed  by  strong  acids,  yielding  ethereal  salts  (esters). 
Are  acted  on  by  CI  and  Br  forming  substitution  products. 

Class  IV.  Aldehydes: — Homologous  series  of  general 
formula  Cn  Han+i-CHO.  Derived  from  primary  alcohols  by 
removal  of  two  atoms  of  H  from  the  — CH2OH  group. 
Examples,  formaldehyde  H.CHO  or  CH2O,  acetaldehyde 
CH3.CHO,  or  QH,0  since  (CH3.CH2.0H)+0=(CH3. 
CH0)+H20.  Up  to  C11H22O  are  colorless,  mobile,  neutral 
volatile  liquids  of  irritating  smell.  Combine  directly  with 
two  monad  atoms.     Are  readily  reduced  and  oxidized. 

Acetals  are  combinations  which  aldehydes  form  with 
alcohols  with  elimination  of  water. 

Certain  substances  used  as  hypnotics  may  be  mentioned 
here: 

Paraldehyde  (C2H40)3,  is  a  polymeric  form  of  aldehyde 
as  can  be  seen  from  its  formula.  It  may  be  prepared  from 
aldehyde  by  treating  the  latter  with  a  little  HCl  or 
with  H2SO4  or  ZnClj. 

Chloral  {not  chloral  hydrate^  is  trichloraldehyde,  CCI3.C 
OH,  made  by  action  of  chlorine  on  alcohol.  Combined 
with  water  it  forms  chloral  hydrate, 

CCI3.COH+H2O. 

Chloralamide  (chloralformamide)  CClg.CHO.HCONHj 
is  a  compound  of  chloral  and  formamide,  HCO.NH2. 

Hypnal  is  a  combination  of  chloral  and  antipyrin,  mono- 
chloral-antipyrin . 

Butyl  Chloral,  C4H5CI3O,  combines  with  water  to  form  a 
hydrate. 

J/<?//y//^2/,HCH/^Q^p^^  is  an  acetal  ohu'med  by  oxidiz- 


ORGANIC    CHEMISTRY.  225 

ing  methyl  alcohol  with  H.^SO^  and  MnOj,  fractioning 
the  product,  and  collecting  the  fraction  boiling  between 
40°  and  50°. 

Class  V.  Ketones.  Derived  from  the  secondary  alco- 
hols by  the  removal  of  two  atoms  of  hydrogen  from  the 
>•  CH, OH  group.  General  formula,  R.CO.R*,  in  which 
R  and  R'  may  be  the  same  or  different  radicals. 

Among  the  more  important  ketones  are  acetone  (dimet- 
hyl ketone)  (CH3),  CO, and  propione  (C2H5)2CO. 

The  former  occurs  in  the  urine,  blood,  and  secretions 
Both  aldehydes  and  ketones  may  be  regarded  as  derived 
from  the  parafifins,  by  substituting  one  atom  of  O  for  two 
of  H;  they  are  therefore,  isomeric.  In  the  case  of  alde- 
hydes two  atoms  of  H  take  the  place  of  one  of  the  CH3 — 
groups,  but  in  the  case  of  ketones  the  O  atom  is  substi- 
tuted for  two  H  atoms  of  a  — CH2 —  group. 

Class  TI.  Fatty  Acids.  Monobasic,  saturated,  prod- 
ucts of  the  complete  oxidation  of  the  alcohol  radical 
CH3,  and  characterized  by  the  group  CO. OH.  The  prin- 
cipal members  of  this  group  with  their  formulas  are 

Formic  acid  CHO.OH. 

Acetic  acid  C2H3O.OH 

Propionic  acid  C3H5O.OH 

Butyric  acid  C^H.O.OH 

Valeric  acid  C5H9O.OH 

Caproic  acid  CeHjiO.OH 

Palmitic  acid  CieHgiO.OH 
Stearic  acid  CjgHssO.OH. 
The  fatty  acids  are  very  stable  but   undergo   double 
decomposition  because  of  carboxyl  group.     Lower  mem- 
bers are  liquids,  grow  oily  on  going  up  the  series  and 
from  C10H20O2  up  are  solids. 

Certain  liquids  of  peculiar  odors  may  be  mentioned 
here: — 


226  DENTAL   CHEMISTRY. 

Propionic  acid,  C3H5O.OH  or  CjHj  COOH,  occurs  in  the 
urine  and  in  perspiration. 

Butyric  acid,  C4H7O.OH  or  C3H7.COOH,  is  found  in  the 
free  state  in  rancid  butter,  in  perspiration,  in  the  contents 
of  the  intestines,  and  in  faeces. 

Valenc  acid,  C5H9O.OH  or  C4H9.COOH  occurs  in  crude 
wood  vinegar. 

Isovaleric  acid  A Y[    ^^CH.CHjCOOH  is  found  in  the 

faeces  and  is  a  product  of  the  decomposition  of  albumin- 
oids. It  may  be  readily  obtained  by  oxidation  of  the 
amyl  alcohol  of  fermentation  by  aid  of  sulphuric  acid  and 
potassium  dichromate. 

Valerianates  are  salts  of  valeric  acid.  Those  of  ammon- 
ium, iron,  and  zinc  are  used  in  medicine. 

Caproic  acid,  CgHiiO.OH  or  CsHn-COOH  is  produced 
in  butyric  fermentation  of  sugar  and  in  the  oxidation  of 
albuminoids. 

Among  the  higher  fatty  acids  we  find 

Palmitic  acid,  CieHgiO.OH  or  CjsHsi.COOH,  in  palm 
oil;  is  a  solid  occurring  in  white  scales. 

Stearic  acid,  CigHgsO.OH  or  C17H35.COOH,  ahard,  white 
somewhat  glossy  solid,  odorless,  tasteless,  and  insoluble 
in  water,  melting  at  69.2 °C. 

Deriyatives  of  the  fatty  acids:  All  the  fatty  acids, 
except  formic,  may  be  converted  into  acid  chlorides,  bro- 
mides, etc. 

Acetyl  chloride,  for  example,  may  be  made  by  adding 
phosphorus  pentachloride  to  anhydrous  acetic  acid. 

All  the  fatty  acids,  except  formic,  may  be  converted 
into  anhydrides  by  treating  the  acid  chloride  with  an  alkali 
salt.  Acetic  anhydride,  (CH3.CO)20.,  for  example,  may  be 
prepared  by  heating  the  anhydrous  alkali   acetates  with 


ORGANIC    CHEMISTRY.  227 

phosphorus  oxychloride,  acetyl  chloride  being  first 
formed  which  interacts  with  more  salt,  forming  acetic 
anhydride. 

Fatty  acids  may  be  converted  into  amides.  Thus  aceta- 
mide,  CH3.CO.NH2,  may  be  produced  by  heating  ethyl 
acetate  with  concentrated  ammonia  under  pressure  ;y^;7«- 
amide  by  distilling  ammonium  formate,  etc. 

Acetic  acid  yields  three  substitution  products  on 
treatment  with  chlorine  in  sunlight:  of  these  the  most  im- 
portant is  trichloracetic  acid  CCI3.COOH,  though  this  is 
best  prepared  by  oxidizing  the  corresponding  aldehyde, 
chloral,  with  concentrated  nitric  acid.  It  is  used  in  med- 
icine in  the  quantitative  determination  of  albumen,  and  as 
an  antiseptic  in  dentistry. 

Fatty  acid  derivatives  include  ^»«/^(?-y^/(y/2^?^.y  as  amido- 
acetic  acid,  CH2(NH2).COOH,  or  "glycocoll";  amido- 
caproic  acid,  C5Hio(NH2).COOH,  or  "leucin".  Both  are 
decomposition  products  of  albuminoids. 

Fats: — Ethereal  salts  resulting  from  combination  of 
fatty  acids  with  the  tri-acid  ^/r^^r*?/,  C3H5(OH)3,  after  the 
analogy  of  tri-acid  bismuth  hydroxide,  thus: 

C3H5(OH)3+3CH3.COOH  =  C3H5(O.CO.CH3)3+3H20 
Glycerol  plus  acetic  acid  equal  glyceryl  acetate  (triacetin) 
and  water,  just  as  Bi(OH3)+3HCl=:BiCl3+3H20. 

Tripalmitin  is  a  compound  of  glycerol  and  palmitic  acid; 
tristearin  of  glycerol  and  stearic  acid;  triolein  of  glycerol 
and  oleic  acid*.  Fats  are  composed  chiefly  of  these  three 
substances  and  are  solid  when  the  first  two  predominate, 
liquid  when  composed  chiefly  of  triolein. 

Soaps  are  formed  when  the  glycerol  compounds  above 
mentioned  (glycerides)  are  decomposed  by  treatment 
with  alkalies,  glycerol  being  liberated,  thus: 


♦Oleic  acid,  CnHssCOOH,  unsaturated,  not  a  fatty  acid. 


228  DENTAL    CHEMISTRY. 

(  0C«H3.0 

C3H5  <  OQeHaiO  +3NaOH 

(  0C,eH3.0 

(OH 
=  C3H5-^  OH  +3C,6H3,OONa 
(OH 
Tripalmitin  plus  sodium  hydroxide  give  glycerol  and 
sodium  palmitate  or  palm-oil  soap.     Again 
(  OC1SH33O 
2C3H5-^  OCi8H330+3PbO+3H20= 
(  OC1SH33O 
(  OH 
2C3H5-^OH+3(Pb2C,8H,^0,) 
(OH 
Triolein,  litharge,  and  water    give  glycerol  and  lead 
oleate,  the  latter  being  what  is  called  lead  plaster. 

Oleo-margarine  is  a  pasty  mass  of  oleic,  palmitic,  and 
stearic  acids  separated  from  stearin. 

Butter  when  pure  contains  about  92  per  cent,  of  a  mix- 
ture of  tristearin,  tripalmitin,  and  triolein;  also  about  'j.'j 
per  cent,  of  tributyrin  the  glyceride  of  butyric  acid.  Artifi- 
cial butter  or  margarine  is  made  from  oleomargarine  by 
churning  with  milk  and  addition  of  butter  color  and  salt. 
Butterine  contains  neutral  lard,  added  to  the  oleo  oil  and 
milk  before  churning. 

Class  VII.  Esters  or  Ethereal  Salts:—* 

Compounds  of  alcohols  with  acids. 

Halogen  ethereal  salts: — identical  with  halogen  mono- 
substitution  products  of  the  paraffins.  May  be  prepared 
by  treating  paraffins  as  methane,  ethane,  etc.,  with  CI  or 
Br  in  presence  of  sun-light;  colorless,  neutral,  pleasant- 
smelling  liquids  except  methyl  chloride,  CH3CI,  which  is 
a  gas.  The  following  esters  (liquids)  are  anaesthetics: — 
ethyl  chloride ,  C2H5CI,  ethyl  bromide,  CjHsBr;  [also  the  deriv. 

•Called  also  "compound  ethers". 


ORGANIC    CHEMISTRY.  229 

stives  methylene  chloride,  CH2CI2,  ethylene  chloride  ox  Dutch 
liquid,  C2H4CI2,  and  ethylidene  chloride  C2H4CI]. 

[Chloroform,  CHCla,  iodoform  CHI3,  Carbon  tetrachloride, 
CCI4,  are  closely  related  to  the  above  in  constitution]. 

Esters    of  nitfic     and    nitrous    acids: — Ethyl     nitrate, 

C2H5.NO3,    a    colorless    liquid;   ethyl    nitrite,    C2H5NO2, 

liquid,  in  alcoholic  solution   known   as  "sweet  spirit  of 

nitre."     Amyl  nitrite  or    iso-amyl-nitrite,   CjHnO.NO,  is 

described  in  section   403.    Ethereal  salts  of  sulphuric  acid 

C  W  ^^-^ 
include  sulphovinic  acid,     ^tt^JI^SOi. 

Mercaptans  and  sidphides : — Compounds  of  hydric  sulph- 
ide with  alcohols;  the  mercaptans  are  ^y<a?n?sulphides= 
Sulphonal  and  trional  are  related  to  ethyl  mercaptan, 
C2H5.SH. 

Ethereal  salts  oforga?iic  acids  include  such  compounds  as 
methyl  butyrate  C3H7.COOCH3,  or  "pear  oil."  Ethyl  aceto- 
acetate,  CH3.CO.CH2.COOC2H5  is  a  similar  compound 
and  is  of  great  importance  in  the  synthesis  of  ketones 
and  fatty  acids. 

Class  VIII.  Alkyl*  compounds  of  nitrogen,  arse- 
nic, etc. 

Amines: — Formed  by  introduction  of  an  alcohol  or 
basic  radical  into  the  ammonia  molecule:  thus,  methyl- 
amine  NH2.CH3  in  which  CH3  is  substituted  for  H  in  NH3, 
hence  a /nw^r^  amine;  dimethylamine,  (CH3)2NH,  is  a 
secondary  amine  since  two  atoms  of  hydrogen  have 
been  replaced;  trimethylamine,  (CH3)N,  is  a  tertiary 
amine.  Amides  and  imides  substitute  acid  radicals  in 
place  of  hydrogen  atoms  in  ammonia:  thus,  formamide, 
HCO.NH2,  and  acetamide,  CHgO.NH.^. 

Various  amine  derivatives: — neurin,  trimethyl-vinyl  am- 
monium hydrate,  N(CH3)3C2H3.  OH,  containing  the  unsat- 

*Alkyl  is  the  term  given  the  alcohol  radicals,  methyl,  ethyl,  etc.  See  table  25, 
section  359. 


230  DENTAL    CHEMISTRY. 

urated  radical  vinyl.  Choline  or bilineurin,  trimethyl-oxethyl 
ammonium  hydrate,  N(CH3)3(C2H40H).OH  found  in  the 
brain  as  lecithin,  in  combination  with  glycerol-phosphoric 
acid.  "■  Piperazine"  is  diethylene-diamine,  (C2H4)2NH2. 
''Putrescin"  is  tetramethylene-diamine,  QH8(N  1^2)2.  ''Cad- 
averine''  is  pentamethylene-diamine  C5Hiu(NH2)2.  Phos- 
phines  are  alkyl  substitution  products  of  PH3,  thus 
methyl  phosphine,  PH2.CH3.     Arsines,  stibines,  etc.,  also 

As  (CH3)2 
occur.     Cacodyl  IS    \  or  diarsenic  tetramethyl. 

As  (CH3)2 

Class  IX.  Glycols  or  Diatomic  Alcohols : — dihydroxy 
derivatives  of  the  paraffins. 

Form  homologous  series.  General  formula,  CnH2n  (OH)2, 
closely  related  to  monohydric  alcohols.  Among  their 
oxidation  products  we  find  glyoxal,  glycocollic  acid, 
lactic  acid,  and  oxalic,  succinic,  malic,  tartaric,  and  citric 
acids.     Double  tertiary  glycols  are  called  "pinacones." 

Class  X.  Trihydric  or  triatomic  alcohols  or  glycer- 
ins :— 

Formed  by  replacement  of  three  atoms  of  hydrogen  in 
a  paraffin  by  OH  groups.  Such  alcohols  act  like  triacid 
bases  and  can  combine  with  one,  two,  or  three  molecules 
of  a  monobasic  acid.  Glycerin  is  prop eny I  glycerin,  C3H5 
(OH) 3,  also  CdX\&^  glycerol.  Nitro- glycerin,  is  glycerol  tri- 
nitrate, C3H5(O.N02),an  ethereal  salt. 

Unsaturated  compounds  related  to  glycerol  are  allyl  alcohol^ 
CHgtCH.CHj.OH,  etc.,  acrolein  or  acralclehyde,  CHj'.CH. 
CHO,  acrylic  acid,  CHaiCH.COOH. 

Class  XI.  Carbohydrates:  Composed  of  carbon,  hy- 
drogen, and  oxygen  in  which  the  ratio  of  H  to  O  is  the 
same  as  in  water:  sugars,  starches,  celluloses.    (Sec.  387). 

Class  XII.  Cyanogen  compounds. 

Derived  from  cyanogen  (CN),  like  chlorides  from  Clj. 


ORGANIC    CHEMISTRY.  231 

Hydrocyanic  acid,  HCN,  potassium  cyanide,   KCN,  like 
hydrochloric  acid,  HCl,  and  potassium  chloride,  KCl.* 

Nitriles  are  ethereal  salts  of  HCN,  as  methyl  cyanide 
or  acetonitrile,  CH3.CN. 

Substances  related  to  cyanogen: — Urea,  CH4N2O,  t^i'io 
acid,  C5H4N4O3,  glycine  (amido-acetic  acid)  CH.^ 
(NHO.COOH. 

Substances  related  to  uric  acid: — Xanthine,  C5H4N4O2, 
guanine,  C5H5N5O,  hypoxanthine,  C5H4N4O.  Gruanidine  is 
an  amidine  of  carbonic  acid,  CH5N3;  creatine,  QH9N3O2, 
and  creatinine,  C4H-N3O,  are  related  to  guanidine. 

Class  XIII.  Furfur ane,  Thiophene,  Pyrrol.  [These 
substances  are  transition  compounds  between  open-chain 
hydrocarbons,  which  have  been  discussed  in  the  preceding 
pages  and  the  aromatic  or  closed-chain  hydrocarbons.  In 
the  latter,  six  atoms  of  carbon  seem  to  join  together  in  the 
closed-chain  structure  and  this  molecule  holds  together 
through  many  reactions]. 

Pyrrol,  QH4NH,  is  obtained  from  coal-tar. 

Tetraiodopyrrol,  C4I4NH,  is  known  as  "iodol." 

Antipyrin,  CnHijN^O,  seems  to  be  a  derivative  of  the 
yet  unknown  pyrazol  which  is  related  to  pyrrol. 

Furfurane,  C4H4O,  and  thiophene,  C4H4S,  are  two  other 
compounds  showing  a   closed  chain  structure  with  less 
than  six  carbon  atoms.     Thus: 
CH^CH^  CH=CH.  CH=CH^ 

I         >o        I         >s  I         \nh 

ch=ch/         ch=ch/  ch=ch^ 

Furfurane.  Thiophene.  Pyrrol. 

All  three  are  liquids  showing  analogous  color  reactions. 


♦Ferrocyanides  and  (erricyanides;  see  Table  4;  sulphocyanates  see  Table  6. 


232  DENTAL    CHEMISTRY. 

Class  XIV.  Aromatics  of  one  nucleus. 

Benzene  series  of  hydrocarboTis : — the  type  is  CoHe,  benzene 
(not  benzine).  Its  graphic  formula  is 

CH 


HC  CH 

I  II 

HC  CH 


CH 
in  which  there  is  alternate  single  and  double  linking. 
Homologues  are  formed  by  replacement  of  one  or  more 
of  the  six  hydrogen  atoms  by  methyl  and  ethyl  groups: 
— thus,  toluene  CeHj.CHa,  the  xylenes  C6H4(CH3)2  etc. 
They  are  coal  tar  products. 

The  unsaturated  hydrocarbons  of  this  series  are  formed  by 
replacement  of  a  hydrogen  atom  of  ethylene  by  a  benzene 
radical,  as  phenyl,  CeHj,  seen  in  styrene  (phenyl-ethy- 
lene, C6H5.CH=CH2,)  dind  phenyl-acetylene  CgHs.C^CH. 

Halogen  derivatives: — chloro-benzene  CsHjCl,  bromo- 
benzene  CeHsBr,  etc.,  benzyl  chloride,  benzal  chloride, 
and  benzo-trichloride  are  related  to  these. 

Sidphonic  derivatives  contain  the  monad  group  HSO3, 
thus  phenol-sulphonic  acid  C6H4(OH)HS03. 

Nitro  derivatives  contain  the  monad  group  NO2,  attach- 
ing itself  to  the  nucleus  and  not  to  the  side-group, 

Nitro-benzetie,  CsHj.NOa,  or  "  mirbane  oil"  is  an  impor- 
tant compound. 

Amido  derivatives  may  be  regarded  either  as  benzene 
in  which  NHj  is  substituted  or  ammonia  into  which  CgHj 
enters.  Thus  aniline,  CeHjNHa,  may  be  regarded  as 
either  amido-benzene  or  phenylamine.  It  is  a  colorless, 
oily  liquid,  acting  as  a  weak  base,  Sulphanilic  acid  is 
para-amido-benzene-sulphonic  acid,  C6Hi(HS03).NH2,  a 
substituted  aniline  with  replacement  in  the  nucleus. 


ORGANIC   CHEMISTRY.  233 

Methyl- aniline  C6H5.NH(CH3)  is  a  substituted  aniline 
with  basic  group  in  side-chain. 

Anilids  are  substituted  anilines  with  acid  groups  in  side- 
chain:  aceianilid,  C6H5.NH(C2H30),  or  "antifebrin"  is 
an  example. 

Para-bromacetanilid,  (J6H4BrNH(C2H30),  is  known  as 
"Asepsin"  or  "antisepsin."  Methyl- acetanilid,  CsHj. 
N(CH3)  (C2H3O),  is  known  as  "exalgin." 

Among  secondary  monami?ies\sdiphenylamine,  (C6H5)2.NH, 
used  as  a  reagent  for  nitrites  in  water  analysis. 

Diazo  andazo  compounds: — Both  contain  the  dyad  group 
—  N  =  N  — ,  linking  in  the  former  a  hydrocarbon  radical  with 
an  acid,  as  diazo-benzene  nitrate,  C6H5.N=N.N03,  in  the 
latter  two  hydrocarbon  radicals,  as  azo-benzene  CeHs— N= 

N-CeHs. 

Aromatic  hydrazines: — Are  derivatives  of  hydrazine, 
NH2—NH2,  formed  by  replacement  of  hydrogen  atoms  by 
alcohol  radicals,  \h\x's,,  phenyl  hydrazi7te,  CeHj.NH  — NHj, 
which  form  with  sugars  hydrazoties  and  osazones.  '^Hydra- 
ceti?i"  is  acetyl-phenyl-hydrazid,  CeHj.NH  — NH(C2H30). 
"Antithermin"  is    phenyl-hydrazine-levulinic   acid,  CeHj. 

/CH3 
NH.N=CC  .CH2-COOH. 

\CH2 

"  Agathine"  is  a  preparation  of  salicylic  aldehyde  and 
methyl-phenyl-hydrazine. 

Phenols: — Hydroxyl  derivatives  of  the  benzene  ser- 
ies in  which  the  OH  group  replaces  a  hydrogen  atom 
of  the  nucleus,  thus  phenol,  CeHj.OH.  They  are  notoxi- 
dizable  without  decomposition.  Phenol  (carbolic  acid)  is 
a  monatomic  phenol.  Among  its  derivatives  are  trichlor- 
phenol,  CeHaCls.OH;  tribromphenol,  C6H2Br3.0H;  nitro- 
phenols,  2js. picric  acid  (trinitro-phenol)  C6H2(N02)3.0H; 
amido-phenols;  phenetidins,   as    acetparaphenetidin     or 


234  DENTAL    CHEMISTRY. 

"P^enacetin,"  C^HA^^q^YI^q.    glycocoll-phenetidin    or 

"phenoco/l;"  phenol-sulphonic  acid,  ortho  ("aseptol"  or 
sozolic  acid)  HSO3.C6H4.OH5  called  also  sulphocarbolic 
acid,  and  its  salts  sulphocarbolates. 

Among  the  homologues  of  phenol  are  the  cresols, 
C6H4(CH3).OH.     Derivatives  of  the  latter  are  thymol  or 

13  4 

para-propyl-meta-cresol,  CeHg.CHs.OH.CsH^;  aristol  or 
dithymoldi-iodide,  C20H24O2I2;  carvacrol,  or  para-pro- 

12  4 

pyl-ortho-cresol,  C6H3.CH3.OH.C3H7. 

Diatomic  phenols  include  pyrocatcchin,  C6Hi{OH)  2,  g'uaiacol 

(  OH 
CeHi^Qz-TT       resorcin,    C6H4(OH)2,     and    hydroguinone, 

C6H4(OH)2.;  orcin  or  dioxy-toluene  C6H3(CH3)(OH)2 
from  which  is  derived  orcein,  C7H7N03,to  which  litmus  is 

related;  creosol,  C6H3(CH3)  \  qqh  ^°""^  ^^^^  guaiacol 
in  beech-wood  tar;  eugenol,  C6H3(OH)2(CH2.CH=CH2) 
a  methyl  ether  of  an  unsaturated  phenol. 

Triatomic phenols  include  the  three  isomers, /yn7^,a//t?/, 
phloroglucine,  and  oxyhydro-quinone,  C6H3(OH)3. 

Pentatomic  phenols:  among  these  are  inosite,  CeHijOe, 
found  in  the  organs  of  the  body  and  sometimes  in  urine. 

Quifiones: — A  class  of  benzene  derivatives  in  which  two 
hydrogen  atoms  seem  to  be  replaced  by  two  oxygen  ones. 
Quifione,  C6H4O2,  is  perhaps  a  ketone  ofadihydro-benzene. 
Chloranil  is  tetrachlor-quinone,  CeCl^Oa. 

Aromatic  alcohols: — Are  hydro xyl  derivatives  of  the 
benzene  series,  in  which  the  OH  group  replaces  hydrogen 
of  the  side  group,  instead  of  that  of  the  nucleus.  They  are 
primary  alcohols  containing  the  group  —CH2.OH  hence 
can  be  oxidized  to  aldehydes  and  acids.  Bejizyl  alcohol, 
CeHj.CHaOH,  when  oxidized  yields  first  befvsaldehyde, 
CeHs.COH,  and  then  benzoic  acid  CeHj.COOH. 


ORGANIC    CHEMISTRY.  235 

Benzaldehyde  is  "oil  of  bitter  almonds;"  condensed  with 
sodium  acetate  it  forms  cinnamic  acid. 

Aromatic  ketones: — Are  analogous  to  the  methane 
ketones:  aceto-phenone  or  "hypnone"  is  CeHs.CO-CHj; 
gallaceto—pheiw7ie  is  C6H2(OH)3.COCH3. 

Phenol  alcohols: — Are  called  oxy  alcohols;  contain  at 
least  two  OH  groups,  one  of  which  (the  phenolic  OH)  is 
directly  attached  to  the  nucleus,  and  the  other  (the 
alcoholic  OH)  is  contained  in  the  side  group,  which  will 
then  be  CHgOH.  Their  empirical  formulas  differ  by  one 
additional  oxygen  atom  from  their  corresponding  aro- 
matic alcohols. 

Phe?iol  aldehydes: — Called  oxy  aldehydes;  contain,  be- 
sides the  aldehyde  group  COH,  the  phenolic  OH.  Scdicyl 
aldehyde,  C6H4(OH)COH,  is  an  example.  Vanillin  is 
methyl-protocatechuic  aldehyde, 

(CHO 
CeH3  \  OCH3 

(oh 

Aromatic  acids  and  phenol  acids: — Contain  one  or  more 
carboxylic  groups,  COOH,  linked  either  directly  or  indi- 
rectly with  the  phenyl  group  or  the  benzene  nucleus. 

Benzoic  acid,  CeHg.COOH,  is  an  aromatic,  monobasic, 
saturated  acid;  cimiamic  acid,  C6H5.CH=CH.COOH,  an 
unsaturated,  polybasic  one. 

Salicylic  acid,  (oxybenzoic)  C6H4(OH)COOH  is  a  phe- 
nol acid;  Salolis  phenyl  salicylate,  salophen  is  acetyl-para- 
amido-phenol    salicylate,   Ce  H4(0H)  -  COO.(C6H,NH. 

COCH3). 

Tyrosine  is  an  amido  acid  sometimes  found  in  urine;  its 

formula  is  C6H,(OH).CH2.CH(NH2).COOH.     Gallic  acid 

is  C6H2(OH  )3.COOH ;  Tannic  acid,  C14H10O9.     "Dermatol" 

is  basic  bismuth  gallate,  C6H2(OH3)COOBi(OH)2. 

Class  XV.  Aromaticsof  more  than  one  nucleus. 

These  are  (a)  compounds  in  which  the  several  benzene 


236  DENTAL    CHEMISTRY. 

nuclei  are  joined  together  without  condensation,  and  (b) 
those  in  which  two  or  more  benzene  nuclei  have  been 
condensed  together  to  form  a  new  and  distinctive  nucleus 
or  grouping. 

Compounds  with  uncondensed  nuclei: — 
Triphenyl  methane,  CH  — (C6H5)3,  is  important. 
Malachite  greens  are  diamide  derivatives  of  triphenyl- 
methane;  rosanilines  are  triamide  derivatives,  etc.     The 
phthalein  group  are  derivatives  of  triphenyl-methane-car- 
boxylic  acid,  z.s  phenol  phthalein.  Indigo  is  made  synthet- 
ically  from  i?-nitro-phenyl-propiolic  acid,    C6H4(N02)  — 
C^C.COOH,  when  heated    with  reducing  agents.     The 
graphic   formula  for  indigo  is 
CO  ^CO^ 

^NH/  NH 

Indigo  carmine  is  the  sodium  salt  of  indigo-disulphonic 
acid,  Ci6H8(S03H)2N202,  made  by  treating  indigo  with 
fuming  sulphuric  acid. 

Isatin,  CgHjNOz,  is  an  oxidation  product  of  indigo.  By 
reduction  of  isatin  is  obtained  indoxyl,  CgHjNO,  found  in 

.CHv 
normal  urine.     Indol  CeH^t:^  ^CH      underlies     the 

whole  indigo  group  and  is  a  product  of  pancreatic  fer- 
mentation. 

Skatol,  C6H4/  /CH,  is  found  in  the  faeces,  hav- 

\NH       / 

ing  the  characteristic  odor. 

Compounds  with  tico  condensed  benzene  nuclei: — 
Two  seriesof  hydrocarbons  of  general  formulas  CnHan-^ 
and  CnHan-iS.  derivatives  of  benzene. 

Naphthalene  series: — naphthalene,    CjoHg,  is   a  coal  tar 


ORGANIC    CHEMISTRY.  237 

product,  occurring  in  white,  lustrous  scales.  It  is  used  as 
an  antiseptic,  disinfectant, and  preservative  against  moths; 
on  a  large  scale  for  the  manufacture  of  phthalic  acid,  etc. 

^^  Thermifi' \s  dL.  substitution  derivative  of  naphthaline, 
tetrahydro-beta-naphthylamine. 

The  naphthols,  C10H7.OH,  are  the  simple  hydroxyl  de- 
rivatives of  the  naphthalene  series.  The  Naphtol  of  the 
U,  S,  P.  is  beta-naphthol.  Betol  is  beta-naphthyl- 
salicylate,  a  derivative  of  beta-naphthol.  Its  formula  is 
C6H,(OH)COOQoH,. 

Asaprol  is  beta-naphthol-alpha-mohosulphonate  of  cal- 
cium. 

Alpha  and  Beta- Naphthoic  acids  are  derived  from  hom- 
ologues  of  naphthalene,  as  alpha  and  beta  methyl-naph- 
thalenes. 

Compounds  with  three  condensed  nuclei: — anthracene  is  an 
example,  C14H10,  in  which  formula  we  have  two  benzene 
residues,  CeH^,  united  by  the  group  C2H2  as  the  middle 
nucleus. 

Alizarine  is  ortho-dioxy-anthraquinone, 
CO. 
CeH^^        ^CsHg— (OH)2, 

\co/ 

formed  by  replacement  of  the  hydrogen  m  the  anthra- 
quinone  formula  by  an  OH  group,  "Turkey  red"  is  made 
from  alizarine. 

6Vi?'y5o/?Aamc  acic?,  CuH5(CH3)(OH)202,  is  a  hydroxyl 
derivative  of  an  anthracene  homologue  methyl-anthra- 
cene. Chrysarobin,  C20H26O7,  found  in  Goa  powder,  is 
related*  to  chrysophanic  acid  as  anthrarobin  is  related 
to  alizarine. 

Compounds  containing  nitrogen  in  the  benzene  nucleus: — 
Pyridine,  C5H5N,  results  from  replacement  of  one  triad 
group,  CH,  in  the  benzene  molecule.  It  is  a  coal-tar 
product.     "Collidines"  are  tri-methyl  pyridines. 


238  DENTAL    CHEMISTRY. 

Piperidine  is  an  hydrogen  addition  product  of  pyridine^ 
C5N5N.H6,  or  hexahydropyridine.  Coniine  the  poison- 
ous principle  of  hemlock  is  dextro-rotatory-alpha-nor- 
mal propyl-piperidine,  C5HioN(C3H7). 

Nicotine^  CioHuNj,  is  hexahydro-dipyridyl  C,oH8(H6)N2. 
Tropine,  cocaine,  and  ecgonine  are  hydrogenated  pyri- 
dine derivatives. 

Quinoline,  C9H7N,  results  from  the  replacement  of  one 
triad  group,  CH,  in  the  naphthalene  molecule  by  the 
element  nitrogen.  It  is  a  pale-yellowish  liquid,  (See  sec- 
tion 453). 

"Kairine"  is  a  quinoline  derivative.  "Thalline"  is  the  sul- 
phate of  a  base  tetrahydro-paraquinanisol,  C9Hio(OCH3)N. 

•' Diaphtherine"  is  a  compound  of  one  molecule  of 
aseptol  with  two  of  ortho-oxy-quinoline. 

"Analgene"  is  another  quinoline  derivative.  "  Orexine" 
is  the  chlorhydrate  of  phenyldihydro  -  quinazoline, 
CuHj2N2.HCl+2HO. 

Class  XYI.  Alkaloids:  see  section  448. 

Class  XVII.  Ptomaines^  leucomaines,  toxalbumins. 

Ptomaines  are  putrefactive  or  cadaveric  alkaloids. 
They  resemble  vegetable  alkaloids.  Non-poisonous, 
non-oxygenated  liquid  ptomaines  are  methylamine,  dimeth- 
ylamine,trimethylainine,  etc.;  also  mydine,  C^W^^HOfbeta- 
me,C5Hi3N03,/>yocyanme,  CuHhNO^.  Poisonous,  non-oxy- 
genated ptomaines  are  putrescine  C4H12N2,  cadaverine 
CsHuNo,  hydrocollidine  CnHijN,  collidine  CeH^N,  par- 
voline  CJl^^N ,  iyrotoxicon  CeHsNj  or  C6H!5.N  =  N.  Oxyen- 
ated  ptomaines  which  are  poisonous  are  neurine  C5H13NO, 
choline  C5H15NO2,  muscarine  C5H,5N03,  gadinine  CvH^NOa, 
mytilotoxine  Q^y^O^,  tetanine  C13H30N2O4,  spasmotoxine, 
typhotoxine  CtH^NOz.  Poisonous  ptomaines  are  some- 
times called  toxines. 


ORGANIC    CHEMISTERY. 


239 


Leucomaines  are  basic  substances  found  in  living  tissues 
either  as  the  products  of  fermentative  changes  or  of 
retrograde  metamorphosis.  Vaughan  gives  the  following 
table:— 

Table  of  Leucomaines. 


Formula. 

Name. 

Discoverer. 

Source. 

Physiological  action. 

C5H5N5 

Adenine. 

Kossel. 

Nucle  in-con- 
taining organs. 

Non-poisonous;  muscle 
stimulant. 

C5H4N4O 

Hypoxanthine. 

Scherer. 

Nu  cl  e  i  n-c  0  n- 
taining  organs. 

Non-poisonous;  muscle 
stimulant. 

C6H5N5O 

Guanine. 

Unger. 

Nucle  in-con- 
taining organs, 
guano. 

Non-poisonous;  muscle 
stimulant. 

C5H4N4O2 

Xanthine. 

Marcet. 

Nu  c  1  e  i  n-c  0  n- 
taining  organs, 
calculi. 

Non-poisonous;  muscle 
stimulant. 

CeHeN^Oa 

Heteroxanthine. 

Salomon. 

Urine. 

C7H8N4O2 

Paraxanthine. 

Thudichum 
Salomon. 

Poisonous. 

C7H8N4O3 

Carnine. 

Weidel. 

Liebig's  meat 
extract. 

Non-poisonous;  muscle 
stimulant. 

C4H5N5O 

Pseudoxanthine(  ?) 

■  Gautier. 

Muscle. 

C6H,4N2 

Gerontine. 

Grandis. 

Liver  of  dogs. 

Poisonous. 

CsHsNC?) 

Spermine. 

Schreiner. 

Sperma,  in  tis- 
sues of  leuco- 
cythsemics. 

Non-poisonous. 

CsHgN*© 

Cruso-creatinine. 

Gautier. 

Muscle. 

C6H10N4O 

Xantho-creatinine 

•' 

" 

Poisonous. 

C9H19N7O4 

Amphi-creatine. 

" 

" 

C11H24N10O5 

Unnamed. 

" 

•* 

C,oH25Nn05 

" 

" 

t* 

C7H,2N402 

" 

Pouchet. 

Urine. 

C3H5N02 

** 

" 

" 

C34H60N2O5 

Salamandarine. 

Zalesky. 

Salamander. 

Poisonous. 

Toxalbumins: — A  group  of  bacterial  proteids  formed 
by  action  of  micro-organisms  on  albuminous  matter. 
They  resemble  the  normal  proteids,  Class  XVIII.  Among 
them  are  the  proteid  poison  of  diphtheria  obtained  as  a 


240  DENTAL    CHEMISTRY. 

white,  amorphous  powder  from  cultures  of  the  Loeffler 
diphtheria  bacillus,  an  intensely  poisonous  substance; 
others  are  the  proteids  from  cultures  of  the  tetanus 
bacillus,  cholera  bacillus,  typhoid  bacillus,  etc. 
Antitoxins  dixe.  bodies  of  unknown  chemical  composition, 
thought  to  be  nucleins,  which  have  the  power  to  protect 
the  individual  against  attacks  of  the  disease  during  prog- 
ress of  which  they  were  formed.  They  are  made  from  the 
blood-serum  of  animals  which  have  recovered  from  infec- 
tious diseases,  as  tetanus  or  diphtheria.  The  name 
"antitoxin"  is  given  to  the  diphtheria  antitoxin. 

Class  XVIIl.  Proteids,  See  section  470  and  also 
the  part  on  Physiological  Chemistry,  Chapter  XV. 

Class  XIX.  Ferments.  See  section  476  and  also  the 
part  on  Physiological  Chemistry,  Chapter  XV. 

The  student  is  now  ready  to  study  at  greater  length 
the  preparation  and  properties  of  important  organic  com- 
pounds as  follows: 

314.    Hydrocarbons. 

Group  1.  Paraffins:  the  general  formula 
for  this  series  is  CnH2n+2.  which  means  that, 
however  many  carbon  atoms  a  paraffin  con- 
tains, it  will  contain  twice  as  many  hydrogen 
atoms  and  two  more.  Thus  marsh  gas,  a  mem- 
ber of  this  series,  contains  one  atom  of  carbon  ; 
one  multiplied  by  two  and  two  added  to  the 
product  equals  four,  therefore  the  number  of 
hydrogen  atoms  xs/our,  and  the  formula  is  CH,. 


ORGANIC    CHEMISTRY.  241 

American  petroleum  contains  many  members  of  this 
series.  They  are  isolated  from  petroleum  hy  fractional 
distillation.  This  process  may  be  conducted  in  the  fol- 
lowing manner:  the  liquid  to  be  distilled  is  placed  in  a 
retort,  through  the  tubulure  of  which  a  thermometer 
passes  to  indicate  the  temperature  at  which  the  sub- 
stance boils.  The  first  portion,  which  distills  over,  will 
consist  chiefly  of  that  liquid  which  has  the  lowest  boiling 
point,  and,  if  the  receiver  be  changed  at  stated  intervals 
corresponding  to  a  certain  rise  in  the  temperature,  a 
series  of  liquids  will  be  obtained,  containing  substances 
the  boiling-points  of  which  lie  within  the  limits  of  tem- 
perature between  which  such  liquids  are  collected. 

315.  Petroleum  or  Mineral  Oil : — 

This  substance,  known  as  rock  oil  or  liquid  bitumeti,  is  a 
natural  product,  consisting  of  a  number  of  hydrocarbons,* 
together  with  small  quantities  of  sulphuretted,  oxygen- 
ized, and  nitrogenized  bodies.  It  contains  about  85  per 
cent,  of  carbon,  and  15  of  hydrogen. 

316.  Among  the  products  obtained  from  petroleum 
are  rhigolene,  gasoline,  naphtha,  benzine,  kerosene.f 

317.  Rhigolene:  one  of  the  lighter  products  of  petro- 
leum, sp.  gr.  from  0.590  to  0.625.  Highly  volatile,  inflam- 
mable, boils  at  70® F,  colorless,  odorless,  when  pure.     It 


*  These  are  homologous  derivatives  of  CH4  up  to  about  C16H34. 

"I"  In  distilling  the  crude  oil,  naphtha,  benzine,  rhigolene,  etc., 
being  the  lightest  come  over  first;  then  at  greater  heat,  kerosene; 
the  residue  is  composed  of  the  heaviest  compounds  which  require 
high  heat  for  their  distillation:  namely,  lubricating  oil,  vaseline, 
paraffine,  etc. 


242  DENTAL   CHEMISTRY. 

is  used  for  producing  local  anaesthesia.  Most  specimens 
of  it  have  a  disagreeable  odor  of  petroleum.  It  should 
be  kept  in  a  cool  place,  in  a  tightly  stoppered  flask,  and 
should  not  be  brought  near  a  light  nor  used  at  all  at 
night. 

318.  Gasoline:  this  substance  is  the  lightest  and  most 
volatile  portion  of  petroleum  "naphtha,"  and  is  employed 
for  napthalizing  gas  and  air.  Its  specific  gravity  is  from 
0.650100.665.     It  boils  at  119° F. 

319.  Naphtha  has  a  density  of  from  0.695  ^o  0-705. 
and  is  often  an  adulterant  of  kerosene. 

Mineral  Naphtha  or  "benzine":  this  substance 
should  not  be  confused  with  henzene.  "Benzine"  is  a 
petroleum  product,  while  benzene  is  a  coal-tar  product. 
The  synonyms  of  "benzine"  are  petroleum  spirit,  petro- 
leum naphtha,  shale  naphtha,  benzoline. 

It  is  a  thin,  colorless  liquid  of  0.69  to  0.74  sp.  gr.,  in- 
flammable, volatile.  It  dissolves  gutta  percha,  naptha- 
lin,  paraffin  wax,  and  many  similar  substances.  It  is 
used  as  an  illuminating  agent  in  sponge  lamps. 

320.  Mineral  burning  oil  or  kerosene:  American 
petroleum  yields  from  50  to  70  per  cent,  of  its  weight  of 
kerosene,  which  is  also  called  refined  petroleum,  photo- 
gene,  and  paraffin  oil. 

It  is  a  solvent  of  sulphur,  iodine,  phosphorus,  cam- 
phor, wax,  fats,  many  resins.  It  softens  india-rubber 
to  a  glairy  varnish.  Its  sp.  gr.  is  from  0.78  to  0.82.  Good 
lamp  oil  should  neither  be  too  viscous  nor  too  volatile, 
and  should  have  a  tolerably  high  boiling  point.  Cold  oil 
of  good  quality  will  not  take  fire,  when  a  light  is  applied 
to  it,  nor  should  its  vapor  inflame.  New  York  State  law 
declares  that  oils  used  for  illuminating  purposes  shall  not 


ORGANIC   CHEMISTRY.  243 

give  a  vapor  that  will  "  flash"  below   ioo°F.,  nor   shall 
themselves  ignite  below  300  F. 

321.    Yaselene  or  vaseline. — 

Synonyms:  cosmolene,  saxolene,  petroleum 
jelly. 

Theoretical  constitution:  vaselene  is  a  7nix- 
ture  of  hydrocarbons,  consisting"  chiefly  of 
those  whose  formulae  are  from  CieHg*  to  C20H42, 
together  with  some  of  the  olefine  series. 

Preparations:  vaselene  consists  of  those 
portions  of  petroleum  which,  at  ordinary  tem- 
peratures, are  soft  or  pasty.  The  last  distill- 
ate or  the  undistilled  portion  is  treated  with 
superheated  steam,  and  filtered  through  ani- 
mal charcoal. 

Properties  and  uses:  colorless  or  pale  yel- 
low, odorless,  translucent,  slightly  fluorescent, 
neutral,  semi-solid.  Its  sp.  gr.,  when  melted, 
is  0.840  to  0.866,  and  it  melts  from  95°F.  to  104°. 
It  is  insoluble  in  water,  nearly  in  alcohol, 
freely  soluble  in  ether,  chloroform,  benzene, 
carbon  disulphide,  and  turpentine.  It  is  mis- 
cible  in  all  proportions  with  fixed  and  volatile 
oils.  It  forms  an  intimate  mixture  with  gly- 
cerine. It  dissolves  sulphur,  iodine,  bromine, 
carbolic  acid,  atropine,  strychnine,  phosphorus, 
benzoic  acid,  and  iodoform,  the  last  best  when 
w^armed.  //  can  not  be  saponified,  nor  does  it 
become  rancid;  hence  is  a  valuable  agent  in 
ointments.     It  is  but  little  affected  by  chemical 


244  DENTAL   CHEMISTRY, 

reagents.  //  is  a  valuable  substitute  for  lard 
in  the  i>rei)aration  of  ointments  cojttaining  sul- 
phur, the  iodides,  compotmds  of  lead,  zinc,  and 

mercury. 

Use  in  dentistry:  vaseline  is  used  as  an 
application  to  inflamed  surfaces,  as  a  dressing; 
in  periostitis,  and  as  an  emollient  after  devital- 
ization or  removal  of  dental  pulps. 

322.  Mineral  lubricating  oil:  the  various  products 
known  by  this  title  are  obtained  from  the  less  volatile 
fluid  portions  of  petroleum.  It  consists  chiefly  of  higher 
members  of  the  olefine  series.  Its  color  ranges  from 
pale  yellow,  through  all  shades  of  red,  brown,  green  and 
blue,  to  black.  Good  qualities  have  very  little  taste,  and 
no  marked  smell,  even  when  heated, 

323.  Group  3,  Hydrocarbons  of  the  foiirtJi  series. 
General  "formula,  C„H2„_4, 

[Hydrocarbons  of  the  third  series,  CnH2n-2.  are  of  no  im- 
portance to  the  dentist].  Those  of  the  fourth  series  in- 
clude turpentine  and  a  large  number  of  oils,  essential  or 
volatile  so-called.  These  different  essential  oils  are  most- 
ly isomers  or  polymers,  having  for  a  formula  CioHie,  or 
some  multiple  of  it. 

324.  Oil  of  turpentine:  QoHie,  called  also  spirit  of 
turpentine  and  essence  of  turpentine,  obtained  by  dis- 
tilling turpentine  or  oleo-resinous  juice,  exuding  from  vari- 
ous kinds  of  pine. 

It  is  a  colorless,  mobile  liquid,  having  peculiar,  aro- 
matic and  disagreeable  odor;  acrid,  caustic  taste;  does  not 
mix  with  water;  soluble  in  alcohol;  dissolves  iodine,  sul- 
phur, phosphorus,  fixed  oils,  resins,  etc.;  exposed  to  the 
air  absorbs  oxygen,  becomes  thicker,  finally  resinous. 
After  prolonged  contact  ivith  air  becomes  ozonized.  Sp,  gr., 
0.864.     Boiling  point,  3i2°F.     It  is  miscible  in  all  proper- 


ORGANIC   CHEMISTRY.  245 

tions  with  ether,  or  at  least  very  soluble  in  it,  and  in  car- 
bon disulphide,  chloroform,  benzine,  petroleum  spirit, 
fixed  and  essential  oils.  It  dissolves  fats,  waxes,  resins,  and 
caoutchouc. 

325.  Sanitas  oil  is  made  by  oxidizing  oil  of  turpentine, 
floating  on  water,  by  a  stream  of  heated  air. 

326.  Terpenes,  terpiii,  terebene,  etc.:  there 
has  been  great  confusion  in  regard  to  the 
names  of  these  substances. 

Terpene  is  the  general  name  for  hydrocar- 
bons having  CioHie  or  some  multiple  for  their 
composition.  Thus,  for  example,  pure  oil  of 
turpentine,  CioHie,  is  called  a  terpene.  \Cam- 
f)hene  has  been  used  as  a  general  term  for  ter- 
penes,  but  it  is  also  used  for  a  particular  kind 
of  terpene']. 

Terpene  is  not  the  same  as  terpin  orterpine; 
terpin  is  a  particular  member  of  the  group  to 
which  the  general  name  terpene  is  given.  Ter- 
ebene is  a  terpene.  Terpenes  are  either  natu- 
ral or  artificial:  the  natural  terpenes  occur  in 
oil  of  turpentine;  the  artificial  are  camphene, 
terebene,  menthene,  cajuputene,  etc.,  etc.  The 
derivative  from  French  oil  of  turpenti^ie  only 
is  called  terpene  hydrate.  Derivatives  from 
any  oil  of  turpentine  are  terpene  hydrochloride, 
terpin  hydrate,  terpin,  terpinol,  etc.,  etc. 

327.  Terebene:  this  substance,  CioHic,  isomeric   with 

oil  of  turpentine,  is  an  artificial  terpene  produced  by  the 
action  of  sulphuric  acid  on  oil  of  turpentine.  //  is  a  mole- 
cular modificatio7t  of  essence  cf turpentine.     It  is  a  clear,  color- 


240  DENTAL   CHEMISTRY. 

less  liquid  and  an  agreeable  remedy,  having  an  odor  like 
that  of  freshly  sawn  pine  wood.  It  does  not  mix  with 
water.  It  imparts  a  very  distinct  odor  of  violets  to  the 
urine. 

Dr.  Wm.  Murrell,  of  London,  has  employed  terebene 
for  the  last  five  years  and  has  made  experiments  to  ascer- 
tain its  properties.  In  the  proportion  of  one  to  five  hun- 
dred it  checks  fermentation,  and  in  one  to  one  thousand 
prevents  it. 

It  absorbs  oxygen  readily,  and  is  a  disinfectant,  and 
antiseptic.  It  dissolves  in  the  various  essential  oils,  and 
is  a  solvent  for  gutta  percha,  iodine,  and  resins.  It  is 
soluble  in  lo  parts  of  alcohol.  Its  sp.  gr.  is  0.860,  and  it 
boils  at  3I3°F.  Most  commercial  terebenes  are  contami- 
nated with  resin,  turpentine,  and  dioxide  of  hydrogen.  It 
is,  however,  almost  impossible  to  prevent  the  formation  of 
hydrogen  dioxide  in  terebene,  which,  so  far  as  topical 
action  is  concerned,  does  no  harm,  but  is  of  advantage, 
lodol  and  terebene  are  now  used  together  in  proportions 
as  follows:  iodol,  10  grains,  terebene,  i  fluid  ounce. 

Terebene  is  used  in  dentistry  as  an  ajitiscptic,  disinfectant, 
and  stimulant. 

328.  Terpin:  and  terpiii  hydrate :  the  "tcrpin"  used 
in  medicine  should  preferably  be  called  tcrpin  hydrate,  as 
it  is  not  properly  terpin.  Nor  is  it  by  any  means  tcr\)ene 
hydrate.  The  substance  now  used  as  an  expectorant  is 
C10H16  (H20)2,  HjO.  It  occurs  in  large,  transparent 
crystals. 

329.  Essential  or  volatile  oils  r'^*  theoretical 
constitution:  most  of  the  volatile  oils  of  plants 
are  terpcues,  that  is,  hydrocarbons  of  formula 
CioHic;  others  are  polymers    of  terpenes   of 

♦Called  essential  6\\%  because  usually  the  fragrant  essence  of  planes 
especially  of  the  flowers. 


ORGANIC   CHEMISTRY.  247 

formula  C15H24.  The  hydrocarbons  of  plants 
are  liable  to  chang;e  in  contact  with  air  or 
moisture,  so  that  they  are  not  found  in  the 
pure  state,  even  when  freshly  obtained.  Some 
essential  oils  consist  mostly  of  certain  ethers, 
some  of  aromatic  aldehydes. 

Preparation:  the  volatile  oils  of  plants  may 
be  obtained  either  by  pressure,  as  in  case  of 
oils  of  laurel,  lemon,  or  bergamot;  \iy  distilla- 
tion with  water,  or  by  passing  a  current  of 
steam  over  the  matter  to  be  extracted;  by 
feri)ientatio)i  and  distillation,  as  with  oils  of 
mustard  and  bitter  almonds;  by  solution  in  a 
fixed  oil. 

General  properties:  essential  oils  of  plants 
are  liquid  at  ordinary  temperatures,  but  de- 
posit solid  matters  in  severe  cold.  Usually 
Hghter  than  water,  colorless  or  yellow,  rapidly 
darkening"  and  ultimately  becoming  resinoid, 
of  marked  and  highly  characteristic  odor, 
readily  combustible,  nearly  insoluble  in  loater, 
freely  soluble  in  alcohol,  miscible  in  all  propor- 
tions with  carbon  disulphide,  fixed  oils,  turpen- 
tine, and  petroleum  spirit;  as  a  rule  not 
saponified  nor  acted  on  by  alkalies,  but 
destroyed  by  strong  nitric  or  sulphuric  acid. 
They  may  be  separated  from  their  alcoholic 
solutionsf  by  addition  of  water  or  solution  of 

■fAn  alcoholic  solution  of  a  number  of  these  oils  is  czMi^^s^  cologne. 


248 


DENTAL   CHEMISTRY. 


sodium  sulphate.  They  are  very  often  adul- 
terated with  alcohol,  chloroform,  oil  of  turpen- 
tine, and  fixed  oils.  Cheaper  essential  oils  are 
often  mixed  with  the  more  expensive.  Essen- 
tial oils  are  gradually  affected  by  exposure  to 
air,  some  oxygen  being  absorbed,  while  at  the 
same  time  a  peculiar  resin  is  formed.  This 
oxidizing  action  is  attended  by  development 
of  ozone.  If  a  spray  of  one  of  these  oils  be 
discharged  into  a  room  where  there  is  plenty 
of  sunlight,  enough  ozone  is  generated  to 
purify  the  air. 

It  is  likely  that  the  oxidation  and  change  of  these  oils 
is  due  to  the  presence  of  small  traces  of  water.  Mr.  John 
Williams  has  obtained  anhydrous  essential  oils,  by  means 
of  apparatus  in  which  the  oils  were  distilled  without  pres- 
ence of  water. 

330.  Anise  oils:  the  Saxon  oil  is  the  best,  though  the 
Russian  is  much  liked.  The  official,  Oleum  Anisi,  is 
colorless  or  yellowish,  with  the  peculiar  odor  and  taste  of 
the  seed.  Its  sp.  gr.  is  0.976  to  0.990,  increasing  by  age. 
At  50°-59°F.  it  solidifies,  but  is  fluid  at  62''.6.  It  is  solu- 
ble in  an  equal  weight  of  alcohol. 

331.  Bergamot:01eum  Bergamii.  It  is  of  sweet,  very 
agreeable  odor,  and  of  bitter,  aromatic,  pungent  taste.  In 
color  the  oil  is  pale  green-yellow.  The  reaction  is  slight- 
ly acid.     It  is  soluble  in  alcohol. 

332.  Cajiiput:  this  oil  is  transparent,  w^ithliv^ely,  pene- 
trating, camphor-like  odor,  of  green  color,  and  warm,  pun- 
gent taste.  The  green  color  is  due  to  copper,  sometimes 
to  chlorophyll.  It  is  met  with  of  a  greenish  color,  even 
when  no  copper  is  present.  A  specimen  of  Paris  oil  con- 
tained, according  to  Guibourt,  0.022  per  cent,  of  copper. 


ORGAiNIC   CHEMISTRY.  249 

Cajuput  oil  is  used  in  dentistry  as  a  local  application  in 
odontalgia,  and  in  neuralgia.  Oleum  Cajuputi  is  the  offi- 
cial name. 

333.  Caraway:  this  oil,  Oleum  Cari,  is  somewhat  vis- 
cid, pale  yellow,  becoming  brownish  with  age,  with  odor  of 
the  fruit,  and  of  aromatic,  acrid  taste.  It  consists  of  two 
liquid  oils,  carvcne  and  carvol,  is  of  neutral  reaction,  and 
soluble  in  alcohol. 

334.  Carvacrol :  obtained  by  treating  caraway  oil  with 
iodine,  and  washing  the  product  with  caustic  potash. 
Pure  carvacrol  is  a  viscid,  colorless  oil,  nearly  insoluble  in 
water,  of  an  odor  like  creasote,  and  of  strong,  acrid,  per- 
sistent taste.  It  is  lighter  than  water.  It  is  antiseptic, 
disinfectant,  and  escharotic.  It  is  used  in  dentistry 
locally  in  odontalgia,  where  there  is  sensitive  dentine, 
alveolar  abscess,  as  an  antiseptic,  and  in  gargles.  It  dis- 
solves Hill's  Stopping  and  gutta  percha. 

335.  Cinnamon:  obtained  by  distillation  from  cinna- 
mon, of  a  light  yellow  color  when  freshly  prepared,  be- 
coming deeper  by  age  and  finally  red.  It  has  a  pungent, 
hot  taste.  It  is  used  in  dentistry  locally,  for  relief  of 
odontalgia. 

336.  Cloves:  the  oil  of  cloves  contains  a 
cedreite  or  hydrocarbon  having"  the  formula 
C15H24,  and  called  caryophyllin.  It  contains 
other  substances,  as  tannin,  resin,  and  an  oxy- 
genized oil  called  eiigenol,  or  eugenic  acid. 
Oil  of  cloves  is  clear  and  colorless  when 
freshly  prepared,  but  yellow  and  finally  red- 
dish-brown on  exposure.  It  has  a  hot,  aro- 
matic taste,  and  the  odor  of  cloves.  Good 
Zanzibar  cloves  yield  about  i8  per  cent,  of  oil. 
Oil  of  cloves  is  used  to  disguise  the  odor  of 


250  DENTAL   CHEMISTRY. 

carbolic    acid,   creasote,   etc.      It  is  used  in 
dentistry  to  relieve  odontalgia. 

337.  Eucalyptus:  the  oil  of  eucalyptus  is  colorless  or 
very  pale,  yellowish,  of  characteristic  aromatic  odor,  and 
pungent,  spicy,  cooling  taste,  neutral  in  reaction  and 
soluble  in  alcohol.  The  official  name  is  Oleum  Eucal- 
ypti. 

338.  Eugenol:  C10H12O2,  an  oxidized  oil,  prepared  by 
decomposing  potassium  eugenate  with  sulphuric  acid.  It 
is  properly  an  acid,  and  will  be  considered  under  the 
head  of  acids. 

339.  Lavender:  this  oil  is  obtained  from  the  flowers 
of  Lavandula  vera,  and  is  of  a  pale-yellow  color. 

340.  Oil  of  Oaultheria  is  a  stimulant,  volatile  oil 
from  the  leaves  of  Gaulthena  procumbens,  first  colorless, 
gradually  becoming  reddish,  and  one  of  the  heaviest  of 
the  volatile  oils.  About  90  per  cent,  of  the  oil  is  com- 
posed of  the  so-called  methyl  salicylate,  (CH3(C7H503). 
The    formula     of     salicylic     acid     is    CvHgOs;     that   of 

methyl  salicylate,  C,  ]  /-tt     [  O3. 

341.  Mint:  oil  of  peppermint.  Oleum  Menthae  Piper- 
itse,  is  of  greenish-yellow  color,  becoming  reddish  by  age. 
It  has  a  strong  aromatic  odor,  and  a  warm,  camphorous, 
pungent  taste,  succeeded  by  a  sensation  of  coolness, 
when  air  is  drawn  into  the  mouth. 

342.  Neroli:  the  oil  obtained  from  orange  flowers  is 
termed  oil  of  neroli,  and  is  a  volatile  oil  of  delightful 
odor. 

343.  Pyrethrum:  the  oil  dissolved  in  ether  is  used  in 
odontalgia.  Pyrethrum  or  pellitory  is  a  powerful  local 
irritant. 

344.  Rose:  this  substance,  known  dXso  ■&.?,  attar  ox  ottar 
of  rose,  is  nearly  colorless,  concrete  below  8o°F.,  liquid 
between  84°  and  86°F.     It  has  a  powerful  and  diffusive 


ORGANIC    CHEMISTRY.  251 

odor,  is  slightly  soluble  in  alcohol,  and  of  a  slightly  acid 
reaction.  The  official  name  is  Oleum  Rosae.  Probably 
all  the  oil  of  rose  of  the  Turkish  market  is  adulterated. 
It  should,  when  slowly  cooled  to  50°F.,  deposit  a  crystal- 
line substance,  called  a  stcaropten,  free  frpm  oxygen. 

345.  India-rubber:  caoutchouc  or  India- 
rubber  is  the  dried,  milky  juice  obtained 
from  several  trees  growing  in  the  tropics. 
When  freshly  obtained  the  juice  is  acid  in 
reaction.  It  contains  several  hydrocarbons 
which  are  soluble  in  ether,  benzole,  carbon 
disulphide,  chloroform,  and  turpentine,  but 
insoluble  in  water  and  in  alcohol.  It  is  hard 
and  tough  in  the  cold,  softens  on  neating,  be- 
comes elastic,  melts,  and,  on  cooling,  is  soft 
and  viscid.  It  combines  directly  with  sulphur, 
hardening,  and  forming  Y ulcaiiized  India-rub- 
ber; carbon  disulphide  is  used  to  facilitate 
the  union.  Mixed  with  half  its  weight  of  sul- 
phur, Vulcanite  or  Ebonite  is  formed.* 

Dental  rubber:  India-rubber  is  prepared 
for  vulcanizing  by  incorporating  with  it  either 
sulphur  alone,  or  some  of  its  compounds;  a 
coloring  matter  is  also  added,  in  many  cases 
mercuric  sulphide  (vermilion)  but  white  clay, 
oxide  of  zinc,  and  calcium  carbonate  are  also 
used.  Para  rubber  is  the  kind  used,  the  ver- 
milion being  added  when  a  "  red  rubber"  is 
desired,  and  the  oxide  of  zinc  or  some  form  of 

*  Both  India-rubber  and  gutta-percha  resist  the  action  of  most 
chemical  substances,  and  hence  are  dissolved  with  difficulty. 


252  DENTAL   CHEMISTRY. 

aluminium  silicate,  as  white  clay,  when  a 
"white  rubber."  "Black  rubbers"  are  the 
result  of  vulcanizing-  the  rubber  directly  with 
sulphur,  no  pigment  being  added.  It  is 
claimed  that  the  various  pigments,  when  in 
larg-e  percentage,  produce  soft,  inflexible  rub- 
bers. Difference  in  shade  of  red  is  supposed 
to  be  due  to  difference  in  percentage  and  kind 
of  vermilion  used. 

346.  Gutta-percha  resembles  caoutchouc- 
in  chemical  characters,  and  is  the  hardened 
milky  juice  of  an  Indian  tree.  It  is  harder 
than  rubber  and  less  elastic,  but  becomes  quite 
soft  in  hot  water,  and  can  then  be  moulded. 
When  purified  it  is  brown-red,  of  a  density  of 
0.979,  electrified  by  friction,  and  is  a  very  slow 
conductor  of  electricity.  It  has,  at  ordinary 
temperatures,  considerable  tenacity,  is  as 
strong-  as  leather  but  less  flexible.  At  i  i5°F., 
it  is  pasty  and  still  very  tenacious.  At  103'' 
and  i04°F.,  it  may  be  spread  out  into  sheets, 
or  drawn  out  into  threads  or  tubes.  Its  sup- 
pleness and  ductility  diminish  as  the  temper- 
ature is  lowered,  and  it  has  not  at  any  tem- 
perature the  elastic  extensibility  of  caout- 
chouc. Softened  by  heat,  it  may  be  worked 
by  pressure  into  any  shape.  It  is  soluble  in 
carbo7i  disulphide,  benzene,  chloroform,  in  hot 
oil  of  turpentine.  //  is  iitsolMe  in  water,  in 
which  it  is  best  preserved,  resists  alkalies,  hy- 


ORGANIC   CHEMISTRY.  253 

drochloric  acid,  and  hydrofluoric  acid.  Gutta- 
percha alters,  and  this  fact  must  not  be  for- 
gotten. If  in  thin  sheets  or  threads,  at  a 
temperature  of  from  77°  to  86°F.,  it  gradually 
becomes  useless  and  gives  off  a  pungent  odor. 
The  change  is  due  to  oxidation. 

Use  in  dentistry:  gutta-percha  is  used  as  a 
plastic  filling  material.  It  is  an  ingredient  of 
Hill's  Stopping.  Together  with  oxide  of  zinc, 
it  is  used  as  a  filling  material.  According  to 
Flagg  it  is  easy  to  raise  the  gutta-percha  to 
any  reasonable  degree  of  temperature  at 
which  it  becomes  plastic,  by  simply  increasing 
the  relative  quantity  of  inorganic  admixture, 
but  this  very  increase  is  destructive  to  the 
value  of  the  gutta-percha. 

As  found  it  is  often  adulterated,  but  owing  to  advanced 
knowledge  pure  gutta-percha  can  be  more  readily  ob- 
tained than  formerly.  We  have  to  distinguish  between 
two  forms  of  adulteration,  those  used  for  the  purpose  of 
fraud  in  weight, — that  is,  foreign  substances  such  as 
small  stones,  sand,  and  pieces  of  bark;  and,  second,  those 
that  combine  with  it  to  injure  its  strength, — pitch,  tar, 
etc.  But,  strange  to  say,  none  of  these  latter  interfere 
with  its  hardness  when  cold.  This  last  adulteration  the 
dentist  has  to  guard  against,  and  therefore  to  test  its 
strength  it  should  be  slightly  warmed.  The  two  best 
grades  are  known  to  the  trade  as  "  G.  P.  A."  and  "  G.  P. 
F,"  The  G.  P.  A.  is  of  a  light-brown  color,  and  the  G.  P. 
F.,  when  sheeted,  is  a  beautiful  marbled  white.  (Meriam). 

For  dark-colored  stopping  Meriam  uses  G.  P.  A.,  and 
for  light,  G.  P.  F.,  and  for  medium,  the  two  mixed. 


254  DENTAL    CHEMISTRY. 

For  convenience  they  had  best  be  bought  sheeted, 
keeping  in  mind  that  the  different  forms  in  which  it  is 
offered  do  not  indicate  different  varieties.  The  gutta 
percha  should  always  be  fresh,  and  feel  soft  and  unctuous 
in  handling. 

The  splint  gutta  percha,  often  called  pure,  which  is 
occasionally  recommended,  is  adulterated  with  tar  or 
resin,  and  it  can  readily  be  seen  that  such  adulteration 
must  injure  its  fibre. 

Pure  gutta  percha  can  be  obtained  by  dissolving  in 
chloroform,  drawing  off  with  a  siphon,  and  then  distill- 
ingoff  the  chloroform,  or  dissolving  in  disulphide  of  carbon 
and  filtering  through  animal  charcoal.  These  methods  need 
not  be  used  to-day,  as  G.  P,  F.  sheeted  will  be  found  white 
enough  for  all  purposes.     (Meriam). 

Meriam  uses  oils  for  softening  the  surface. 

347.  Artificial  gutta  perchas  are  now  made.  Accord- 
ing to  Zingler  copal  resin,  sulphur,  petroleum,  casein, 
tannin,  and  ammonia  are  the  substances  used  in  manufac- 
ture. 

348.  Camphor. — 

Theoretical  constitution:  CjoHisO.  It  is  sometimes 
classified  among  the  aldehydes,  but  for  convenience  will 
be  considered  among  the  hydrocarbons  on  account  of  its 
oils.  Camphor  is  a  concrete  substance  derived  from 
camphor-laurel  tree  ;  soft,  tough  cakes,  easily  powdered 
on  addition  of  a  little  alcohol;  translucent,  strong  frag- 
rant odor,  aromatic  bitter  cooling  taste,  volatile,  inflam- 
mable; lighter  than  water;  slightly  soluble  in  water,  but 
soluble  in  alcohol,  ether,  chloroform;  dissolved  in  alcohol 
forms  spirit  of  camphor,  from  which  it  may  be  precipitated 
by  water;  dissolved  in  water,  containing  a  little  alcohol 
and  a  little  magnesium  carbonate,  forms  cmnphor-watcr : 
boiled  with  bromine,  forms  mono-hromated  camphor,  C10H15 
BrO.      Gum-camphor  has  a  rotatory  movement  on  water 


ORGANIC    CHEMISTRY.  255 

which  is  stopped  by  the  least  trace  of  fat.  Camphor  is  a 
local  irritant,  stimulant,  and  poison.  It  is  a  constituent 
of  celluloid. 

Spirit  of  camphor  is  locally  employed  in  dentistry  to  allay 
pain.     With  ether  it  is  used  as  a  local  anaesthetic. 

Taken  internally,  it  is  poisonous,  although  recovery 
from  its  effects  are  usual.  The  treatment  consists  in  use 
of  emetics  and  castor  oil. 

349.  The  official  Oleum  Camphor<2  is  made  by  heating 
camphor.  It  is  a  light  reddish-brown  fluid,  of  the  taste 
and  odor  of  camphor. 

350.  Resins,  Balsams,  Gum-resins,  etc.:  resins  are 
oxidized  terpe7ies,  produced  by  the  oxidation  of  the  essen- 
tial oils  of  plants.  They  are  brittle,  solid,  transparent 
bodies,  of  no  well  marked  odor  or  taste,  soluble  in  alco- 
hol, insoluble  in  water,  combustible,  yield  a  lather  with 
alkalies. 

Resins  are  employed  in  the  manufacture  of  varnishes: 
copal  resin  is  prepared  by  simple  exudation. 

351.  (jiiaiacuni  resin  is  prepared  by  destructive  dis- 
tillation, and  in  other  ways,  from  a  tree  growing  in  South 
America  and  the  West  Indies.  It  comes  in  large,  irregu- 
lar, semi-transparent,  brittle  pieces,  externally  of  an  olive 
or  deep  green  color,  internally  red.  It  has  a  slight  bal- 
samic odor,  and  leaves  a  hot  acrid  sensation  in  the  mouth 
and  throat.  It  is  wholly  soluble  in  alcohol,  partly  soluble 
in  water. 

352.  Oum-resins  are  resins  mixed  with  gum,  sugar,  etc., 
inplants,  and  are  insoluble  in  water,  soluble  in  glycerine, 
turpentine,  and  strong  alcohol.  They  are  a  mixture  of 
several  bodies,  hence  have  not  a  definite  chemical 
formula. 

353.  Myrrh  is  an  exudation  from  an  Arab- 
ian or  African  tree,  and  is  a  gum-resin.     It  is 


250  DENTAL    CHEMISTRY. 

of  reddish-yellow  or  reddish-brown  color,  of 
fragrant,  strong,  peculiar  odor,  and  bitter,  aro- 
matic taste.  It  is  translucent,  pulverizable, 
and  brittle.  It  should  dissolve  in  fifteen  times 
its  weight  of  water,  when  rubbed  up  with  an 
equal  weight  of  sal-ammoniac.  It  has  a 
resinous  fracture,  and  makes  a  light  yellowish 
powder.  Inferior  kinds  are  darker,  less  trans- 
lucent, and  less  odorous;  The  resin  of  myrrh 
is  called  myrrhic  acid.  Myrrh  forms  an  emul- 
sion with  water,  and  is  soluble  in  alcohol  and 
in  ether.  An  old  tincture  of  it  has  been  shown 
to  have  an  acid  reaction."^'  It  is  used  in 
dentistry  as  a  local  application.  The  powder 
is  also  used  in  dentifrices. 

354.  Gums  are  non-volatile,  colloid,  almost  tasteless 
bodies,  occurring  in  the  juices  of  plants.  (See  Carbohy- 
drates). 

355.  Sandarach:  sandarach  is  a  substance  composed 
of  three  resins,  which  are  of  different  solubility  in  alco- 
hol, ether,  and  turpentine.  Sandarach  comes  in  tears, 
which  are  small,  and  of  a  pale  yellow  or  brown  color,  and 
more  or  less  transparent:  they  are  dry  and  brittle.  San- 
darach is  inflammable,  and  melts  on  being  heated.  It  is 
soluble  in  alcohol,  ether,  and  warm  oil  of  turpentine.  It 
is  used  in  dentistry,  dissolved  in  alcohol,  as  a  varnish. 

The  name  sandarach  is  sometimes  given  to  the  disul- 
phide  of  arsenic,  which,  however,  has  nothing  to  do  with 
the  resin  sandarach,  and  should  not  be  confused  with  it. 

356.  Lac:  lac  consists  of  resin,  soluble  coloring  matter, 
lacin,  wax,  and  salts.      The  resin  is  about  90  per  cent,  of 

♦Brackett. 


ORGANIC   CHEMISTRY.  257 

lac.  Shell  Lac  is  one  of  the  commercial  varieties  of  lac, 
and  is  an  exudate  from  several  kinds  of  trees  growing  in 
the  East  Indies;  it  is  caused  by  punctures  of  insects.  It 
is  prepared  from  the  crude  lac  by  melting,  straining,  and 
pouring  on  a  flat,  smooth  surface.  Shellac  comes  in  thin, 
shining,  hard,  brittle  fragments,  odorless,  insoluble  in 
water,  but  freely  soluble  in  alcohol,  more  so  in  warm 
alcohol.     It  is  used  in  dentistry  as  a  varnish. 

357.  Naphthalene:  naphthalene  or  naphthalin,  CjoHg, 
or  (CioH;)H,  is  a  coal  tar  product,  distilling  from  this  sub- 
stance between  356°  F.  and  428°.  It  crystallizes  in  large, 
white,  rhombic  plates,  of  silvery  lustre,  and  characteristic 
odor,  and  of  a  biting,  somewhat  aromatic  taste.  It  melts 
at  174.5"  F.,  and  boils  at  420"  to  428°.  It  volatilizes  very 
sensibly,  even  at  ordinary  temperatures.  It  is  injlatnam- 
hlc,  burning  with  a  luminous  and  very  smoky  flame.  Its 
specific  gravity  is  1.15.  When  melted,  it  dissolves  sul- 
phur, phosphorus,  iodine,  and  indigo.  It  is  insoluble  in 
water,  but  soluble  in  hot  alcohol,  benzene,  and  ether,  also 
in  wood-spirit,  chloroform,  carbon  disulphide,  petroleum 
spirit,  fixed  and  volatile  oils.  It  is  insoluble  in  alkaline 
or  dilute  acid  solutions,  slightly  soluble  in  concentrated 
acetic  acid.  It  is  an  antiseptic  substance,  and,  when  used 
as  dressing,  should  be  thoroughly  purified  by  recrystalliza- 
tion  from  alcohol  or  by  distillation  with  steam.  It  is  not 
corrosive,  and  when  entirely  pure  is  odorless;  it  is,  how- 
ever, almost  impossible  to  obtain  it  free  from  the  charac- 
teristic odor,  but  the  latter  may  be  entirely  overcome  by 
adding  a  few  drops  of  oil  of  bergamot  to  4  oz.  of  the 
naphthalin.  In  powdering  naphthalin,  addition  of  a  lit- 
tle alcohol  greatly  facilitates  the  operation.  As  an  anti- 
septic, the  best  results  have  been  obtained  from  use  of  it 
in  powdered  form.  Combinations  of  this  substance  with 
iodoform  and  with  boric  acid  should  make  valuable  anti- 
septics.    The   naphthalin    made    in  this   country  can  be 


258  DENTAL    CHEMISTRY. 

reduced  to  a  moderately  fine  powder;  the  pure,  Imported 
naphthalin  cannot  be  reduced  to  powder  except  when 
very  cold.  Attention  should  be  paid  to  the  fact  that  it  is 
inflammable. 

358.  Naphtliols:  C10H7O.  There  are  a  number  of  these 
compounds.  What  is  commercially  known  as  "  hydro- 
naphthol,"  is  properly,  bcta-hyd} o-naphtJiol,  has  powerful 
antiseptic  properties  (1-7200  limit)  and  is  iion-poisono7is. 

[That  which  is  called  in  commerce  "  beta-naphthol,"  is 
properly,  according  to  Wolff,  bctanahydro-mxplithol,  and 
according  to  Bouchardat,  Kaposi,  Miner,  Piffard,  and 
others,  is  poisonous.  To  distinguish  them  dissolve  in 
alcohol.  Hydronaphthol  (non-poisonous)  dissolves  in 
10  parts  alcohol,  with  a  deep-brown  coloration,  while 
beta-naphthol  dissolves  without  coloration]. 

Naphthol  used  medicinally  crystallizes  in  thin,  shining 
plates,  readily  soluble  in  alcohol,  ether,  chloroform,  and 
fatty  oils. 

359.  Ethyl  series  of  radicals,  alcohols,  and  carbohy- 
drates. 

Before  considering  the  alcohols,  it  is  well  for  the 
student  to  become  familiar  with  the  ethyl  series  of  radi- 
cals. 

Table  25.    Ethyl  Series  of  Radicals. 

n  J  r)    J-     1  Hydrides  of,  or  Marsh 

Compound  Radicals.  ^  Gase^ 

Methyl,  CH3  Methane,    CH,H    or   CH, 

■p-thwl    r  w  (marsh  gas). 

Ethyl,  QH,  Ethane;  QH^H  or  C,He 

Propyl,  C3H  Propane,  etc. 

Butyl,  C4H9  Ikitane,  etc. 

Amyl,  CsHn  etc.,  etc. 

etc.,  etc.  etc.,  etc. 


ORGANIC   CHEMISTRY.  259 

Table  25 — Continued. 
Oxides  or  Ethers.  Hydrates,  or  Alcohols. 

(CH;02O,  or  CHfiO,  CH3HO,  or  CHA    wood 

methyl  ether.  spirit,  methyl  alcohol. 

(QH5)A   or  QHioO,  QH5HO,  or  QHA  ordin- 

ethyl  ether.  ary  alcohol, 

etc  etc, 

etc.  etc. 

etc.  CsHuHO,  or  C5H12O,  amyl 

etc.  alcohol,  fusel  oil. 

360.  Theoretical  formation:  the  starting  point  in  form- 
ing these  compounds  is  with  the  hydrates  or  alcohols,  and 
not  with  the  compound  radicals  themselves.  For  exam- 
ple, when  an  alcohol,  as  C^HfiO,  is  oxidized  with  oxygen 
limited  in  amount,  there  results  what  is  called  an  aldehyde 
or  dehydrated  alcohol,  as  C2H40,  two  atoms  of  hydrogen 
being  withdrawn  and  no  oxygen  added. 

If,  however,  the  alcohol  is  oxidized  \w\\\\ plentiful oxyge^t, 
an  atom  of  oxyen  is  added  in  place  of  the  two  atoms  of 
hydrogen  withdrawn,  and  an  aeid  is  formed;  thus,  from 
QHgO  comes  CaH^Oa,  or  acetic  acid. 

361.  Tabular  view  of  aldehydes  and  acids  of  ethyl 
series    of  radicals: 

Radicals.  Alcohols.            Aldehydes.               Acids. 

Methvl.  CH3  CH4O                   CHab              CH2O2  (forming 

Ethyl,  C.Hs  C2H6O                   CaHjO                       acid). 

etc.  C)H402  (acetic 

etc.  acid). 

Compounds  of  the  hydrocarbon  radicals  with  chlorine, 

bromine,  etc.,  are  called  haloid  ethers,  while  salts   proper 

of  the   hydrocarbon   radicals  are  called  compound  ethers. 

Ethers  are,'in  general  then,  compounds  of  the  hydrocarbon 

radicals  other  than  the  marsh  gases,  alcohols,  aldehydes, 

and  acids.     (See  section  407). 

362.  Alcohols:'"'  alcohols  may  be  regarded 

*It  will  be  noticed  that  the  chemist's  conception  of  alcohols  in- 
cludes many  substances,  such  as  glycerine,  which  resemble  little  our 
ordinary  alcohol. 


260  DENTAL   CHEMISTRY. 

as  substances  derived  from  hydrocarbons  by 
replacing-  one  or  more  hydrogen  atoms  by  the 
radical  hydroxyl,  HO.  Thus  ethyl  hydride, 
(CaHs)!^,  becomes  ethyl  alcohol,  (C2H5)  HO, 
by  exchanging  one  atom  of  H  for  the  radical 
HO."  Alcohols  are  called  monatomic,  diato- 
mic, or  triatomic,  according  as  HO  replaces 
one,  two,  or  three  atoms  of  H  in  a  hydrocar- 
bon. Ordinary  alcohol  is  a  monatomic  alcohol, 
diatomic  alcohols  are  also  called  glycols,  and 
of  triatomic  alcohols  glycerine  is  a  notable 
example. 

The  alcohols  are  hydrates,  resembling  the 
inorganic  hydrates,  as,  for  example,  potassium 
hydrate,  KHO;  common  alcohol  is  ethyl 
hydrate,  QHs  HO. 

363.    Alcohol.— 

Synonyms:  ethyl  alcohol,  common  alcohol, 
ethyl  hydrate,  ethylic  alcohol.  Spirit  of  Wine. 

Theoretical  constitution:  C2H5HO,  hydrate 
of  the  radical  ethyl,  two  atoms  of  carbon,  six 
of  hydrogen,  and  one  of  oxygen;  formula 
sometimes  written  CaHeO.  Molecular  weight, 
46.  24  parts  by  weight  of  carbon,  6  of  hydro- 
gen, and  16  of  oxygen. 

Preparation:  alcohol  is  obtained  by  the  fer- 
mentation of  saccharine  liquids,  brought  about 
by  the  growth  of  a  microscopic  plant  called 
yeast. 


ORGANIC   CHEMISTRY.  261 

Grape  sugar  or  glucose  yields  alcohol  when 
fermented: 

CeHi^Oe     =     2CO2     +     2C2H5HO 

Glucose  carbon  alcoliol 

dioxide. 

The  fermented  liquid  is  distilled,  and  a  dilute 
alcohol  obtained;  repeated  distillations  will 
finally  give  an  alcohol  containing  about  14  per 
cent,  of  water.  To  obtain  alcohol,  free  from 
from  water,  the  former  must  be  mixed  with 
half  its  weight  of  lime,  and  the  alcohol  distill- 
ed off  from  the  mixture. 

Properties:  absolute  alcohol  containing  no 
water  is  a  transparent,  mobile,  volatile,  color- 
less liquid  of  an  agreeable,  pungent  odor, 
characteristic  of  itself,  and  a  burning  taste, 
boiling  at  173°  F.,  of  a  sp.  gr.  0.794,  ^^^  has 
never  been  solidified.  It  is  neutral  in  reaction, 
inflammable,  burning  with  a  non-linninoiis 
flame,  dissolves  resins,  essential  oils,  alkaline 
hydroxides,  alkaloids,  calcium  chloride,  mer- 
curic chloride,  and  many  other  substances,  but 
especially  those  rich  in  hydrogen.  Mixed  with 
water,  a  contraction  of  volume  occurs,  with 
production  of  heat.  Its  attraction  for  water  is 
very  great;  it  absorbs  moisture  from  the  air 
and  abstracts  it  from  membranes,  tissues,  etc. 
Shaken  with  pure,  colorless  sulphuric  acid,  it 
should  not  become  colored.  (  Presence  of  fusel 
oil).     It  is  poisonous. 

364.     Absolute   alcohol:    commercial    usage    accepts    as 


262  DENTAL   CHEMISTRY. 

absolute,  alcohol  of  not  less  than  99.5  to  99.7  per  cent,  of 
sp.  gr.  (at  60"  F.)  0.7938,  boiling  at   172.4"  F. 

Alcohol,  U.  S.  P.,  is  91  per  cent,  by  weight  of  real  alco- 
hol, or  94  per  cent,  by  volume,  the  rest  being  water. 

Alcohol  diliitiim  is  45.5  per  cent,  by  weight,  or  53  per 
cent,  by  volume. 

Spirit  of  ivine  {rectified  spirit)   is  84  per  cent,  by  weight. 

Proof-spirit  is  49  per  cent. 

Spirits  are  substances  distilled  from  fermented  liquors; 
brandy,  whisky,  rum,  and  gin  are  examples.  They  con- 
tain from  35  to  45  per  cent,  of  alcohol  by  volume,  although 
some  specimens  run  as  high  as  50  per  cent,  (brandy,  rum) 
and  some  as  high  as  60  per  cent.,  (whisky). 

lVi7ics  contain  from  6  to  25  per  cent.,  sherry  and  port 
being  the  strongest. 

Beers  average  4  to  5  per  cent.,  thougl\  some  are  very 
weak,  containing  only  i  per  cent. 

Use  in  dentistry:  alcohol  is  used  in  dentistry  for  vari- 
ous purposes,  as  styptic,  antiseptic,  obtunding  agent,  for 
drying  cavities,  in  lotions,  gargles,  etc.,  etc.,  and  as  a  sol- 
vent and  preservative. 

Toxicology:  the  stomach  pump  should  be  used  in  cases 
of  poisoning  by  alcohol,  and,  if  the  bladder  is  distended, 
use  of  the  catheter  is  indicated.  Cold  affusion  to  the 
head,  fresh  air,  ammonia,  and  strong  coffee  are  valuable, 
especially  if  the  stupor  be  intense. 

365.  Tinctures  are  alcoholic  solutions  of  the  medicinal 
agents  in  plants,  prepared  by  maceration,  digestion,  or 
percolation. 

366.  Fluid  Extracts :  these  preparations  are  concent- 
rated, and  represent  considerable  drug-power  in  small 
bulk.  Each  Cubic  centimetre  represents  a  gram  of  the 
crude  drug. 

367.  Wood  Spirit:  methyl  alcohol,  or  wood  spirit,  is 
methyl    hydrate,    CH3HO,    called    pyroligneous    ether. 


ORGANIC   CHEMISTRY.  263 

pyroxylic  spirit;  wood  naphtha  is  largely  composed  of  it. 
It  is  made  by  distillation  from  wood.  It  is  a  liquid  of 
spirituous  odor,  and  is  inflammable.* 

368,  Fusel  Oil  is  amylic  alcohol,  C5H11HO,  hydrate  of 
the  radical  amyl,  called  s\so  potato  spirit.  Fusel  oil  pro- 
per is  a  mixture  of  several  alcohols,  of  which  amylic 
alcohol  is  one.  It  is  made  from  residues  left  in  the  still, 
after  common  alcohol  is  distilled  off.  It  has  a  peculiar, 
irritating  odor,  and  is  very  poisonous.  Is  produced  in  the 
fermentation  of  grain,  hence  often  an  impurity  in  whisky. 

369.  Glycerine- 
Theoretical  constitution:  this  substance  is  a 

triatomic  alcohol  deriv^ed  from  propane 
(C3H7)  H,  by  substitution  of  3HO  for  t/ij^ee 
atoms  of  H.  The  formula  for  propane  may- 
be written  CsHs;  take  away  three  atoms  of  H 
and  we  have  C3H5;  add  3HO  and  there  results 
C3H53HO,  or  CsHsOg.  Glycerine  is,  then,  the 
hydrate  of  a  radical,  C3H5,  called  glyceryl, 
friteuyl,  ox  propeuyl.  Hence  the  modern  term 
for  glycerine,  namely,  tritenyl  Jiydrate. 

Properties  and  uses:  glycerine  is  obtained 
from  fats  by  treatment  with  alkalies,  soap  be- 
ing formed  and  glycerine  liberated.  The  pro- 
cess is  called  sapoiiilicrttioii.  Pure  glycerine 
is  a  colorless,  or  light  straw  yellow,  thick, 
syrupy  liquid,  unctuous,  inodorous,  of  sharp, 
sweet  taste;  soluble  in  water,  alcohol,  and  oils, 
but  not  in  ether  or  chloroform.     //  is  valuable 


♦Methylated  spirit  is  composed  of  g  parts  ordinary  alcohol  to  i  part 
wood  alcohol. 


204  DENTAL   CHF.MISTRY. 

as  a  solvent  for  many  medicinal  sttb stances, 
official  solutions  of  which  in  glycerine  are  call- 
ed glycerites.  Glycerine  is  permanent  and 
does  not  evaporate  or  dry  at  any  tempera- 
ture. Official  Glyceriiium  has  a  sp.  gr.  of  i  .25. 
It  dissolves  about  fifty  familiar  substances 
used  in  medicine,  among  which  are  boric  acid, 
borax,  carbolic  acid,  creasote,  potassium 
iodide,  arsenic,  alum,  zinc  salts,  morphine 
salts,  tannate  of  quinine. 

Use  in  dentistry:  its  value  in  dentistry  is  as 
a  solvent,  and  when  combined  with  other  sub- 
stances,, as  an  emollient  and  solvent.  Teeth 
lotions  contain  glycerine,  as  for  example  the 
following:  tincture  of  quillaia,  eau-de-cologne, 
water,  borax,  glycerine,  with  coloring.  Glycer- 
ine is  found  to  be  of  service  in  the  process  of 
vulcanizing  India  rubber,  giving  the  latter  the 
property  of  resisting  oils  and  fats.  Glycerme 
may  be  used  to  detect  carbolic  •  acid  adultera- 
tion in  creasote.     (See  Creasote). 

370.  Glycerites:  these  are  solutions  of  various  sub- 
stances in  glycerine.  Those  most  commonly  used  in 
dentistry  are  the  glycerites  of  carbolic  acid,  gallic  acid,  tan- 
nic acid,*  sodiimi  borate,  stare Ji,  thymol,  and  pepsin. 

The  glycerite  of  borax  (sodium  borate)  becomes  acid 
and  unfit  for  use  after  a  time. 

371.  Boroglyeeride  :  boroglyceride,  C3H5  BO3,  is 
glyceryl  borate,  or  tritenyl  borate,  made  by  heating  boracic 
acid,  H  BO3.  with  glycerine,  C3H53HO,  or  CsHsOj: 

♦The  glycerite  of  tannin  is  used  as  an  application  to  spongy  gums. 


ORGANIC   CHEMISTRY.  205 

CaH^Os     +     H3BO,     +     heat     =     QH^BO,    +    SH^O. 

Glycerine.  boracic  acid.  boroglyceride.  water. 

6  parts  of  boric  acid  in  fine  powder  and  9  of  glycerine 
are  heated  together  in  a  porcelain  dish  at  302*^  F.,  stirring 
well  until  aqueous  vapors  cease  to  be  given  off,  and  a 
homogeneous,  transparent  mass  is  formed,  which  becomes 
hard  and  tough  on  cooling.  Care  is  taken  not  to  heat 
the  mixture  too  strongly,  as  that  would  render  the  pro- 
duct dark  colored.  Boroglyceride  is  a  colorless,  tough, 
solid  substance,  soluble  in  water,  and  in  alcohol,  odorless, 
tasteless,  not  poisonous.  It  is  used  in  dentistry  as  an  anti- 
septic, and,  in  combination  with  sodium  sulphite,  for 
bleaching  teeth. 

372.  Sodium  glyceroborate :  this  substance  is  made 
by  heating  equal  parts  of  sodium  borate  with  glycerine. 
Soluble,  deliquescent,  odorless,  antiseptic. 

373.  Calcium  glyceroborate:  made  by  heating  equal 
parts  of  calcium  borate  with  glycerine.  Soluble,  deliques- 
cent, odorless,  antiseptic. 

374.  Creasote:  creasote,    Creasotum,  is   a 

mixture  of  substances,  but  consists  chiefly  of 
creasol,  CsHioOt,  and  giiaiacol,  CvHsOa.  //  is  a 
product  of  the  distillation  of  wood- tar,  occur- 
ring in  the  lowest  layer  of  the  distilled  liquid. 
It  is  colorless,  or  faintly  yellow,  when  fresh  and 
pure,  of  sp.  gr.  1.046,  U.  S.  P.,  but  usually 
varying  from  i  .040  to  i  .090.  It  boils  at  392°-4 10'' 
F.  //  is  of  disagreeable,  f>enetratiug,  smoky  odor, 
and  burning,  caustic  taste.  It  is  soluble  in  80 
parts  of  cold  water,  and  24  of  hot,  and  in  all  pro- 
portions in  alcohol,  ether,  acetic  acid,  and  car- 
bon disulphide.   Ignited,  it  burns  with  a  white, 


266  DENTAL   CHEMISTRY. 

sooty  flame.  It  forms  a  clear  mixture  with 
collodion;  precipitates  solutions  of  gum  and  of 
albumin.  On  growing  old,  it  gradually  be- 
comes brownish  in  color.  It  may  be  distin- 
guished from  carbolic  acid  by  not  solidifying 
when  cooled,  by  not  coloring  ferric  chloride 
permanently,  by  its  lower  boiling  point,  and 
by  being  insoluble  in  glycerine. 

A  specimen  of  creasote,  if  pure,  should  leave 
no  stain  on  paper,  after  being  dropped  on  it 
and  volatilized  by  heat.  Mixed  with  equal 
volume  of  collodion,  it  should  not  cause  the 
latter  to  gelatinize. 

Creasote  water,  Aqua  Creasoti,  consists  of 
one  fluidrachm  of  creasote  to  one  pint  of 
water.  Solidified  creasote  is  made  from  lo 
parts  of  collodion  to  15  of  creasote. 

Use  in  dentistry:  creasote  is  used  as  an 
obtunding  agent,  styptic,  antiseptic,  to  coun- 
teract any  acid  in  a  tooth  cavity,  to  harden 
the  contents  of  dental  tubuli  and  render 
them  imperishable. 

Toxicology:  creasote  is  poisonous,  in  over- 
doses causing  giddiness,  obscurity  of  vision, 
depressed  heart  action,  etc.,  etc. 

The  treatment  consists  in  administration  of 
white  of  Q,^'g,  milk,  wheat  flour,  and  stimu- 
lants, as  aromatic  spirit  of  ammonia.  An 
emetic  should  be  first  administered. 


ORGANIC    CHEMISTRY.  267 

375.    Plieiiyl  jilcoliol  or  carbolic  acid.—* 

Synonyms:  phenol,  phenylic  alcohol,  phenic 
acid.     Official  name,  Acidum  Carbolicum. 

Theoretical  constitution;  carbolic  "acid"  is 
really  an  alcohol,  CeHgHO,  or  hydrate  of  the 
radical  phenylf,  CgHg,  graphically 

CH— CH 

/  V 

HC.  C-O— H 

\  / 

HC  =  CH 

It  is  by  weight  composed  of  72  parts  carbon, 
6  of  hydrogen,  and  16  of  oxygen.  Molecular 
weight,  94. 

Preparation:  crude  carbolic  acid  is  obtained 
by  distilling  coal-tar  between  the  temperatures 
of  302°F.  and  374°F. 

Official  carbolic  acid  is  a  pure  phenol,  ob- 
tained by  distilling  crude  carbolic  acid  between 
338°F.  and  365°,  separating  from  other  pro- 
ducts, and  purifying  by  repeated  crystalliza- 
tion. 

Properties:  carbolic  acid,  in  the  pure  state, 
forms  needle-shaped,  colorless,  interlacing  crys- 
tals, neutral  in  reaction,  having  a  characteristic, 
slightly  aromatic  odor,  and  pungent,  caustic 
taste;   the  taste  is  sweetish  when  the  acid  is 

*  Called  "  acid"  because  of  its  ready  combination  with  bases  form- 
ing carbolates  or  phenates,  so-called, 
t  This  radical  phenyl  belongs  to  the  aromatic  series. 


268  DENTAL   CHEMISTRY, 

slightly  diluted.  //  ^produces  a  white  eschar  on 
aiwnal  tissues,  having  a  benumbing  {caustic) 
effect.  When  pure,  carbolic  acid  is  permanent 
in  the  air,  and  not  affected  by  light,  but  the 
ordinary  acid  usually  changes  to  pink  or  red. 
The  color  does  not  in  the  least  impair  the 
medicinal  value  of  the  phenol. 

Water  dissolves  6  per  cent,  of  phenol,  according  to 
Squibb.  Five  parts  of  phenol  dissolve  in  i  part  of  alco- 
hol; 4  in  one  of  ether;  3  in  i  of  chloroform;  y  in  2  of 
glycerine ;  4  in  7  of  olive  oil.  It  is  also  soluble  in  benzol, 
carbon  disulphide,  fixed  and  volatile  oils.  Variations  in 
the  melting  and  boiling  points  of  phenol  are  due  to  the 
greater  or  less  proportions  of  water  in  it.  Phenol  is 
liquid  at  ordinary  temperatures,  when  it  contains  8  to  10 
per  cent,  of  water.  The  best  grades  in  the  market  con- 
tain at  least  2  per  cent,  of  water,  and  often  over  4.  One 
volume  of  liquefied  carbolic  acid,  containing  5  per  cent,  of 
water,  forms,  zvith  i  volume  of  glycerine,  a  clear  mixture, 
which  is  not  rendered  turbid  by  the  addition  of  3  volumes 
of  water  (absence  of  creasote  and  cresylic  acid).  Car- 
bolic acid  should  have  no  odor  of  creasote  nor  of  volatile 
sulphur  compounds.  A  clean,  sweet,  phenol  odor  is  one 
of  the  best  signs  of  good  quality  in  carbolic  acid.  It 
should  also  be  hard  and  dry.  An  anhydrous  acid, 
fused  with  from  4  to  5  per  cent,  of  water,  should,  on 
cooling,  become  a  solid  mass  of  crystals  again.  The 
crystals  become  liquid  at  a  temperature  of  from  96.8''F. 
to  197.6°.  When  reddened  and  liquefied,  carbolic  acid 
resembles  creasote,  but  gives,  dissolved  in  water,  a  per- 
7nanent  violet-blue  with  ferric  chloride,  while  creasote 
gives  a  blue  which  chafiges  to  greeji  then  to  brozun.  The 
crystals  may  be  prepared,  for  antiseptic  use,  by  warming 
the  bottle  till  they  liquefy,  then   adding  a  few  drops  of 


ORGANIC   CHEMISTRY.  269 

glycerine.  Carbolic  acid  is  a  valuable  antiseptic.  It  coagu- 
lates albumin  and  is  poisonous.  Death  has  followed  ex- 
ternal application  of  the  acid,  in  large  quantity,  to  exten- 
sive surfaces. 

Use  in  dentistry:  as  an  antiseptic,  disinfect- 
ant, styptic,  escharotic,  obtunding-  agent,  local 
anaesthetic,  etc.,  etc. 

Toxicology:  carbolic  acid  is  a  powerful 
poison,  being  corrosive  and  also  producing; 
coma,  the  acid  being  rapidly  diffused,  and  the 
odor  of  it,  after  death  from  poisoning,  noticed 
everywhere  throughout  the  body,  even  in  the 
brain.  The  treatment  is  to  give  emetics,  as, 
for  example,  apomorphine  hydrochlorate  sub- 
cutaneously,  then  raw  eggs  ad  libitiun,  and 
magnesia  suspended  in  a  mixture  of  olive  and 
castor  oils;  lime  water  with  sugar  is  also 
recommended.  The  coma  must  be  treated  as 
in  cases  of  opium  poisoning,  by  artificial  res- 
piration, galvanism,  etc.,  etc.  Chances  of 
recovery  from  poisonous  doses  of  the  acid  are 
not  good.  The  urine  should  be  watched,  when 
carbolic  acid  is  being  used,  and  if  it  becomes 
dark-colored,  it  is  a  sign  that  too  much  of  the 
agent  is  being  used. 

376.    Tarioiis  preparations  containing  carbolic  acid. 

Robinson's  remedy  is  composed  of  equal  parts  of  caus- 
tic potash  (potassium  hydrate)  and  carbolic  acid,  mixed 
by  trituration. 

Chloral  hydrate  and  carbolic  acid,  when  mixed  in  pro- 
portion of    I    part  of   chloral   to    1.7  parts  of  the   acid, 


270  DENTAL   CHEMISTRY. 

liquefy,  and  the  liquid  is  soluble  in  water  in  all  propor- 
tions. 

377.  Phenates:  carbolic  acid,  with  solutions  of  the 
alkalies,  forms  soluble  compounds  called  phenates  or 
phenylates,  which  are  capable  of  dissolving  large  quanti- 
ties of  phenol. 

378.  Phenol  sodiqueor  sodium  phenate:  this  sub- 
stance, CeHjNaO,  is  also  called  carbolate  of  sodium, 
sodium  phenoxide,  Sodae  Phenas.  It  is  made  by  the 
direct  combination  of  carbolic  acid  with  sodium  oxide; 
caustic  soda  and  a  little  water  are  used  in  the  reaction, 
which  is  as  follows: 

CeHsHO  -f  NaHO  =  CeHsNaO  +  H.O. 

Carbolic  acid  sodium  sodium  water 

hydrate  phenoxide 

Sodium  phenate  occurs  in  form  of  acicular  crystals  of 
light  pinkish  color,  liquefied  by  heat.  It  is  used  in 
dentistry  as  an  astringent,  styptic,  disinfectant,  etc.,  etc. 
It  is  freely  soluble  in  water. 

379.  Phenol  terchloride :  this  substance  is  of  Russian 
introduction,  and  is  extemporaneously  prepared  by  mix- 
ing one  part  of  a  four  per  cent,  solution  of  carbolic  acid 
with  five  parts  of  a  saturated  solution  of  chlorinated 
lime;  the  filtrate  is  said  to  be  25  times  more  powerful 
than  carbolic  acid.  According  to  some  authorities  it 
may  be  made  by  passing  a  stream  of  chlorine  gas 
through  pure  melted  carbolic  acid,  until  a  violet  color  is 
seen. 

Dental  uses:  Phenol  terchloride  is  used  as  an  anti- 
septic and  disinfectant.  It  is  combined  with  iodoform, 
and  used  as  a  capping  and  filling  material,  incorporated 
with  decalcified  dead  bone. 

380.  Phenol-camphor*    is  best   obtained  by   heating 

♦Synonyms:  Carbol-camphor,  Camphor-carbol,  Caiftph'^-Pb';- 
nique. 


ORGANIC   CHEMISTRY.  271 

pure  crystallized  carbolic  acid  (phenol)  until  it  fuses, 
and  then  gradually  adding  gum  camphor;  a  clear  liquid 
is  obtained  which  is  characteristic  on  accojnt  of  its 
permanence.  In  preparing  this  substance,  use  equal 
parts  of  camphor  and  carbolic  acid:  it  remains  liquid  for 
an  indefinite  time,  and  does  not  solidify  on  being  sub- 
jected to  the  low  temperature  of  a  frigorific  mixture  of 
snow  and  sodium  chloride.  Phenol-camphor  [C8HiiO(  ?)] 
is  a  limpid,  colorless,  volatile,  refractive  liquid,  possessing 
the  fragrant  odor  of  camphor,  entirely  extinguishing  the 
one  of  carbolic  acid,  and  has  a  sweetish,  camphoraceous, 
but  biting  taste,  not  as  caustic  as  that  of  carbolic  acid, 
somewhat  benumbing  the  tongue.  It  is  soluble  in  alco- 
hol, ether,  chloroform,  and  ethereal  oils,  but  Insoluble  in 
glycerine  aiui  in  luatcr,  being  heavier  than  the  latter. 
When  ignited  it  burns  with  a  smoky  flame.  There  is 
reason  to  believe  that  it  is  a  chemical  compound.  Dr. 
Schaefer  has  used  phenol-camphor  as  a  local  ancBsthetic  in 
tooth-ache,  introducing  it  on  cotton  into  the  cavity  of  a 
carious  tooth.  This  substance  can  be  likewise  used  as  an 
antiseptic.  It  mixes  well  with  paraffin,  cosmoline,  and  a 
number  of  oils.  In  impregnating  cotton  gauze  (antiseptic 
gauze )  phenol-camphor  maybe  used  as  a  substitute  for 
carbolic  acid.  Phenol-camphor  is  less  irritating,  less 
caustic  than  carbolic  acid,  and  has  also  the  advantage  of 
possessing  a  pleasant  odor.  It  is  used  in  dentifrices. 
381.     Resorcin:    this   substance    has    for   its    formula 

CcHoOo,  or  better    CeH* -,  ttq   from  which  it  will  be  seen 

that  it  differs  from  carbolic  acid,  in  that  the  radical  HO 
has  been  substituted  for  one  atom  of  hydrogen,  carbolic 
acid  being  CgHsHO,  and  resorcin,  CcH^  2HO. 

It  is  made  from  gum-resins,  such  as  galbanum,  extract 
of  sapin  wood,  or  Brazil  wood,  by  fusing  them  with  caus- 
tic potash.     It  occurs  in  the  form  of  colorless  crystals,  of 


272  DENTAL    CHEMISTRY. 

somewhat  sweetish,  slightly  pungent  taste,  very  soluble  in 
water,  less  so  in  alcohol,  ether,  glycerine,  and  vaseline,  in- 
soluble in  chloroform,  and  carbon  disulphide.  It  is  not 
so  irritating  as  carbolic  acid.  It  is  said  to  be  a  disinfect- 
ant and  local  anaesthetic. 

ItisJiscd  in  dentistry  as  an  antiseptic.'^  Strong  solutions 
are  caustic,  but  dilute  ones  merely  astringent. 

382.  Menthol:  this  substance  is  really  inenthyl  alcohol, 
C10H20O,  and  is  found  in  peppermint  oil.  It  is  a  white, 
crystalline  solid  of  but  slight  peppermint-oil  odor  when 
pure,  soluble  in  alcohol,  and  in  the  essential  oils.  It  has 
been  called  peppermint  camphor,  Japanese  camphor, 
peppermint  stearescence,  and  stearoptene  of  peppermint, 
but,  in  constitution,  is  a  monatomic  alcohol.  //  is  an  anti- 
septic and  local  ancBsthctic.  It  is  used  in  dentistry  as  an  ob- 
tunding  agent,  local  anaesthetic,  and  antiseptic.  Gare 
must  be  taken  in  applying  it,  as  small  doses,  taken  in- 
ternally, have  been  known  to  produce  vomiting. 

383.  Eucalyptol:  C12H.V),  liquid,  colorless,  of  aro- 
matic odor.  It  is  derived  from  the  leaves  of  Eucalyptus 
globidus,  and  is  sometimes  called  eucalyptus  oil.  It  is  but 
slightly  soluble  in  water,  but  is  soluble  in  alcohol.  It  is 
an  efficient  antiseptic,  and  is  used  in  dentistry  on  this  ac- 
count, and  as  an  astringent,  styptic,  and  local  ancBsihetic. 
It  has  solvent  action  on  gutta pcrcha.  The  purest ,  eucalyp- 
tol is  as  clear  as  water,  of  specific  gravity  O.910  to  0.920  at 
60*^.,  and  boils  between  338°F.  and  343°.  There  is  in  the 
market  an  eucalyptus  oil  which  differs  from  the  genuine 
eucalyptol;  90  per  cent,  alcohol  makes  a  clear  solution  of 
eucalyptol,  while  the  eucalyptus  oil  is  but  slightly  soluble 
in  it. 

Alantol:  CeoHajO.  A  liquid  stearopten  found  besides 
helenin  in  the  root  of  elecampane. 


*Said  to  be  a  stronger  antiseptic  than  carbolic  acid,  and  not  so 
poisonous. 


ORGANIC   CHEMISTRY.  273 

384.  Myrtol:  myrtol  is  obtained  fiom  the  distillation 
of  the  leaves  of  the  myrtle;  it  is  a  liquid  possessing  the 
characteristic  perfume  of  the  plant.  It  is  of  less  density 
than  water,  evaporates  at  the  ordinary  temperature,  stains 
paper,  but  the  stains  disappear  entirely.  It  has  a  warm, 
slightly  acrid  taste,  soon  followed  by  a  sensation  of  fresh- 
ness. It  is  said  to  be  an  excellent  disinfectant  and  an 
energetic  antiseptic. 

385.  Safrol:  this  substance  is  obtained  by  fractional 
distillation  from  crude  oil  of  camphor.  It  has  a  strong 
sassafras  odor  and  taste,  and  is  used  for  disguising  the 
taste  of  other  substances. 

386.  Thymol:  formula  C10H14O.  There  are  many  thy- 
mols. The  one  found  in  essence  of  wild  thyme  is  used  in 
dentistry,  and  may  be  procured  by  treating  the  essence 
with  potassium  hydrate;  insoluble  in  water,  antiseptic. 
Freely  soluble  in  alcohol.  Used  in  dentistry,  combined 
with  glycerine,  as  an  antiseptic. 

387.  Carbohydrates:  these  are  substances 
containing;  six  atoms  of  carbon,  or  a  multiple 
of  six,  and  twice  as  many  atoms  of  hydrogen 
as  of  oxygen.  They  closely  resemble  the 
alcohols,  and  may  be  divided  into  three  classes: 
saccharoses,  glucoses,  and  amylosesf' 

Of  the  saccharoses,  cane  sugar  and  milk 
sugar  are  important. 

388.  Cane  Sugar:  saccharose,  cane  sugar,  beet  sugar, 
C12H22O11,  does  not  occur  in  the  body;  white,  inodorous, 
very  siveet.  Cold  water  dissolves  three  times  its  weight; 
insoluble  in  alcohol.  Converted  by  ferments  first  into 
mixture    of   glucose    and    Isvulose,    called  invert    sugar. 

"^Saccharin  is  not  a  carbohydrate,  but  the  sulphinide  of  benzoic 
acid.    (See  Benzoic  Acid). 


274  DENTAL    CHEMISTRY. 

Blackens  with  HzSO^,  (Glucose  unites  with  the  acid  and 
does  not  blacken).  Cane  sugar  occurs  in  the  juices  of 
many  plants,  fruits,  flowers,  and  in  honey.  It  is  found 
also  in  the  juice  of  the  sugar  cane,  in  sorghum,  beet-root, 
and  sugar-maple.  TJie  most  soluble  sugar*  as  well  as  the 
sweetest  and  most  crystallizable. 

389.  Milk-sugar:  lactose,  sugar  of  milk,  Saccharum 
Lactis,  C-jHsoOuHX),  one  of  the  constituents  of  milk  of 
mammals;  rarely  found  in  vegetables.  To  prepare  it, 
coagulate  skimmed  milk  with  a  little  acetic  acid,  heat, 
filter,  concentrate  filtrate  by  evaporation,  let  crystallize, 
dissolve  in  boiling  water  and  re-crystallize.  Odorless, 
white,  hard,  occurs  in  four-sided,  rhombic  prisms;  taste 
faijitly  sweet,  gritty  between  the  teeth;  soluble  in  seven 
parts  cold  water,  one  of  boiling;  insoluble  in  even  60  per 
cent,  alcohol;  not  charred  by  HaSOi  ;  not  directly  fer- 
mented by  5'east,  but  easily  when  cheese  is  added;  does 
not  form  a  syrup  with  water.  Used  in  tooth  pozvders  and  in 
triturating  medicines. 

390.  Glucose:  CeHijOg,  is  raisin  sugar  and  grape  sugar; 
it  is  also  called  dextrose  and  starch  sugar.  It  is  found  in 
vegetables,  fruits,  and  honey.  Is  white,  inodorous,  and 
soluble  in  its  own  weight  of  water.  Only  one  third  as  sweet 
as  catie  sugar.  Ferments  directl)'  with  yeast,  and  when  in 
contact  with  decaying  animal  matter.  Made  on  a  large 
scale  from  corn  starch,  by  boiling  with  dilute  sulphuric 
acid,  neutralizing  with  lime,  draining  off  clear  syrup, 
evaporating,  and  allowing  to  crystallize.  Fermented,  it 
decomposes  into  alcohol  and  carbonic  acid.  ]^aluable  re- 
ducing agent. 

391.  The  amyloses  are  starch,  dextrine,  gum,  etc. 
Starch  is  found  in  grains  of  cereals  and  in  potatoes;  is 
food  of  plants  becoming  sugar  as  they  ripen.       Insoluble 

♦Dissolved  in  water  forms  Syrupus  Simplex,  or  simple  syrup. 


ORGANIC   CHEMISTRY.  275 

in  cold  water,  alcohol,  or  ether;  in  boiling  water  it  becomes 
gelatinous,  but  does  not  dissolve  ;  heated  dry  it  becomes 
dextrine,  which  is  converted  into  glucose  by  action  of 
diastase  (a  ferment  found  in  cross-spired  barley). 

Dextrine:  is  an  amorphous,  yellowish-white,  soluble 
substance;  does  not  give  blue  coloration  with  iodine; 
basis  of  mucilage.     Reduces  alkaline  copper  solutions. 

The  formula  for  dextrine  is  probably  CeHjoOs.  That 
of  starch  some  multiple  of  CeHjoOs. 

392.  Honey :  honey  is  practically  a  strong  solution  of 
dextro-glucose  and  Irevo-glucose  in  water.  Analyses  show 
that  the  laevulose  and  dextrose  are  nearly  equal  in 
amount.  Fictitious  honey  is  sometimes  manufactured 
from  glucose  and  flavoring  materials;  the  presence  of 
glucose,  as  an  adulteration,  is  indicated  by  increased  pro- 
portion of  ash,  and  by  the  presence  of  a  notable  amount 
of  calcium  sulphate.  Honeys  are  preparations  of  medici- 
nal substances  in  honey,  the  clarified  article  being  used. 
Honey  of  sodium  borate  contains  a  drachm  of  borax  to  the 
ounce  of  clarified  honey. 

393.  Gnnis :  these  bodies  are  probably  carbohydrates. 
They  are  a  peculiar  class  of  bodies,  occurring  in  the  juices 
of  plants.  They  are  entirely  non-volatile,  of  little  or  no 
taste,  uncrystallizable,  and  colloidal.  They  are  either 
soluble  in  water,  or  swell  up  in  contact  with  it.  They  are 
not  capable  of  being  fermented  by  yeast  and  are  insoluble 
in  alcohol. 

394.  Crum  Arabic  is  the  dried  exudation  from  the  bark 
of  various  species  of  Acacioc.  Picked  Turkey  gum  is  the 
finest,  and  occurs  in  colorless  lumps,  full  of  minute  cracks. 
It  consists  chiefly  of  calcium  arabate,  the  calcium  salt  of 
arabic  or  gummic  acid.  It  is  inodorous,  of  feeble,  slight- 
ly sweetish  taste,  and  with  water  forms  a  viscid  mixture, 
called  a  viucilage.  The  mucilage  is  used  in  dentistry  as 
an  emollient. 


276  DEN.TAL    CHEMISTRY. 

395.  Gum  Tragacanth:  this  is  a  white,  or  yellowish 
substance  which  is  only  very  slightly  soluble  in  water,  and 
swells  up  in  it.  It  contains  usually  about  60  per  cent,  of 
a  substance  which  yields  pec^ic  acid,  also  8  or  10  per  cent, 
of  soluble  gum,  probably  arabin,  the  rest  being  starch, 
cellulose,  water,  etc.,  etc. 

396.  Cellulose:  Ccllulin,  lignin,  CeHioOa,  is  an  isomer  of 
starch,  and  constitutes  the  essential  part  of  the  solid 
framework  or  cellular  tissue  of  plants.  Swedish  filter- 
paper,  linen  rags,  and  cotton  wool  are  more  or  less  pure 
cellulose.  Soluble  only  in  a  solution  of  cupric  oxide  in 
ammonia. 

Absorbent  cotton:  consists  essentially  of  cellulose. 

397.  Collodion  is  made  by  dissolving  4  parts  of  pyroxy- 
lin in  a  mixture  of  26  parts  alcohol  and  70  of  ether. 
Pyroxylin  is  prepared  by  steeping  cotton  in  a  mixture  of 
nitric  and  sulphuric  acids. 

Flexible  collodion  is  collodion  to  which  5  per  cent,  of  tur- 
pentine and  3  per  cent,  of  castor  oil  have  been  added. 

Cantharidal  collodion  is  made  from  powdered  canthar- 
ides  and  flexible  collodion,  with  sometimes  addition  of  a 
little  Venice  turpentine,  to  prevent  contraction  on  drying. 

Iodized  collodion  is  a  solution  of  iodine  in  collodion,  20 
grains  to  the  ounce.  Iodoform  collodion  contains  i  part 
iodoform  to  15  of  collodion. 

Styptic  collodion  contains  20  per  cent,  of  tannic  acid. 

Collodion  is  a  colorless  liquid,  of  ethereal  odor,  and  very 
inflammable;  exposed  to  the  air  it  rapidly  evaporates, 
leaving  a  thin,  transparent,  strongly  contractile  film  of 
dinitro-cellulose,  which  is  insoluble  in  water  or  in  alcohol. 
It  is  precipitated  by  carbolic  acid.  Collodion  is  used  in 
dentistry  as  a  local  application  in  alveolar  abscesses,  in 
combination  with  other  agents  in  odontalgia,  on  cotton  as 
temporary  filling,  as  a  styptic,  etc.,  etc.  A  colored  pre- 
paration of  collodion  is  used  to  coat  the   surface  of  plas- 


ORGANIC   CHEMISTRY.  277 

ter  models.  Collodion,  when  thickened,  may  be  rendered 
thinner  by  dilution  with  a  solution  of  i  part  alcohol  in  3 
parts  ether. 

Cantharidal collodion  \?y  used  as  a  counter-irritant  in  den- 
tal periostitis.  A  German  preparation  of  cantharidal 
collodion  has  been  proposed  by  Dieterich  to  contain — in 
1,900  parts  of  collodion— 3  parts  of  cantharidin  and  97 
of  oil  of  rape.  The  German  blistering  collodion  is 
stronger  than   the  U.  S. 

3q8.  Celluloid:  pyroxylin  is  reduced  to  a 
pulp,  mixed  with  camphor,  oxide  of  zinc,  and 
vermilion,  subjected  to  immense  pressure,  and 
seasoned. 

ETHERS,    GLUCOSIDES,     FATS,     WAXES,     ALDE- 
HYDES, KETONES,  ETC. 

39Q.  Ethers  are  derived,  theoretically,  by 
replacing"  the  hydrogen  atoms  in  water  by  hy- 
drocarbon radicals;  they  are,  therefore,  oxides. 
Ethers  are  either  simple  or  mixed,  according 
as  the  hydrocarbon  radicals  are  alike  or  differ- 
ent; thus  common  ether  is  a  siinple  ether, 
{C.3H5).0,  that  is,  C.H5— O— C.H5,  while 
methyl-ethylic  ether  is  a  mixed  ether  CaHsO, 
that  is,  CH3— O— CHs. 

Haloid  ethers  are  bromides,  chlorides,  etc., 
of  the  hydrocarbon  radicals:  thus,  hydrobromic 
ether  is  CaHgBr,  or  ethyl  bromide.  Compound 
ethers  are  salts  of  the  hydrocarbon  radicals,  as, 
for  example:  methyl  acetate,  CH3(C2H302),  or 
CH3 — O — C2H3O.  Fats  are  compound  ethers, 
in  which  the  hydrocarbon  radical  is  glyceryl— 


DENTAL    CHEMISTRY. 


in  almost  all  cases;  thus,  stearin  is  stearate  oi 
g^lyceryl,  C3H5(Ci8H3502)3. 
400.    Cominoii  Ether.— 

Synonyms:  ethyl  ether,  ethyl  oxide,  vinic 
ether,  sulphuric  ether,  .4ither,  ^ther  Sulphuri- 
cus. 

Theoretical  constitution:  (C2H5Y2O,  or  ethyl 
oxide,  derived  from  H2O  by  substituting  C2H5 
for  each  atom  of  hydrogen;  contains  4  atoms 
of  carbon,  10  of  hydrogen,  and  i  of  oxygen  in 
its  formula;  by  weight,  48  parts  carbon,  10  of 
hydrogen,  and  16  of  oxygen.  Molecular 
weight,  74.    Graphic  formula,  C2H5 — O — C2H5. 

Preparation:  sulphuric  acid  is  used  to  ether- 
ize alcohol,  hence  the  name  sulphuric  ether. 
There  is  not,  however,  any  sulphuric  acid  in 
pure  ether,  i  part  oi  strong  sulphuric  acid  and 
6  or  7  of  commercial  alcohol  are  heated  to 
266°  F.,  in  a  retort,  and  then  alcohol  is  run  in, 
slowly,  by  means  of  a  funnel,  while  the 
temperature  is  kept  between  266°  F.  and  284°, 
and  the  mixture  distilled.  The  liquid  resulting 
from  the  distillation  contains  on  its  surface 
crude  ether,  which,  purified  by  washing,  dried, 
and  redistilled,  is  ready  for  the  market.  The 
reactions  are  as  follows: 

First  stage, 
C2H«H0  +  H2SO,  =  (C2H5)HS04  +  H2O. 

Alcohol  sulphuric  ethyl  sulphuric  water, 

acid.  acid. 


ORGANIC   CHEMISTRY.  279 

Second  stage, 
GH.HSO,  +  C.H5HO  =  (C.H5).0  4-  H2SO. 

Ethyl  sulphuric  alcohol  ether  sulphuric 

acid  acid. 

The  second  equation  shows  that  the  acid  is 
obtained  again,  hence  a  small  quantity  of  sul- 
phuric acid  can  be  used  to  convert  considerable 
alcohol  into  ether.  Ether  for  anaesthetic  pur- 
poses is  further  purified  by  shaking  with  water 
and  contact  with  lime  and  chloride  of  lime. 

Properties:  pure  ether  is  a  mobile,  very  vola- 
tile liquid,  colorless,  limpid,  and  inflammable, 
of  sweetish,  characteristic  odor'^  and  burning 
taste.  It  should  be  kept  in  bottles  closed  by 
ground-glass  stoppers,  as  it  readily  evaporates. 
It  is  soluble  in  lo  volumes  of  water,  and  in 
alcohol  in  all  proportions.  When  fiure  it  dis- 
solves oils,  resins,  many  organic  bodies,  iodine, 
bromine,  sulphur,  phosphorus,  and  mercuric 
chloride.  Ether  should  not  only  be  kept  from 
the  air,  but  also  from  the  light.  Its  vapor  is 
2>^  times  as  heavy  as  air,  therefore  flows,  and 
will  inflame  with  explosion  from  contiguous 
flame.  The  sp.  gr.  of  ether  is  variously  given 
as  0.720,  0.736,  and  0.713;  that  of  stronger  ether, 
.Either  Eortior,  is  0.728.  The  latter  contains 
about  94  per  cent,  of  pure  ether,  and  6  percent, 
of  alcohol.  Ether  used  for  anaesthetic  purposes 
should  not  effect  blue  litmus,  should  leave  no 

*Callecl  ethereal  odor. 


280 


DENTAL    CHEMISTRY. 


residue  when  evaporated  on  a  watch  glass, 
and  should  not  impart  a  blue  color  to  ig;nited 
copper  sulphate.  Samples  should  be  tested 
before  being  used. 

401.  Use  in  dentistry:  ether  is  used  as  an 
anaesthetic,  both  by  inhalation  and  locally ; 
also  as  an  anodyne,  and  in  various  conditions, 
as  aphthae,  etc.    //  is  useful  as  a  solvent. 

Toxicology:  the  treatment,  in  cases  where 
dangerous  symptoms  appear,  is  to  cease  ad- 
ministering the  ether  at  once,  and,  if  the  breath- 
ing begins  to  fail,  to  pull  out  the  tongue,  to  ap- 
ply electricity,  the  poles  being  placed  over  the 
phrenic  nerves  (on  a  line  with  the  4th  cervical 
vertebra)  and  to  try  artificial  respiration.  In 
administering  ether,  the  breathing  should  be 
watched. 

402.  Ethyl  bromide. — 

Synonyms;  bromide  of  ethyl,  hydrobromic  ether,  Ethyl 
Bromidum, 

Theoretical  constitution: '  CaHjBr,  bromide  of  the  radi- 
cal ethyl,  one  molecule  of  ethyl  and  one  atom  of  bro- 
mine, or  two  atoms  of  carbon,  five  of  hydrogen,  and  one 
of  bromine  in  its  molecule.  It  is  one  of  the  so-called 
haloid  ethers  (see  Ethers). 

Preparation,  properties,  etc.:  ethyl  bromide  is  obtained 
by  distilling  potassium  bromide  with  alcohol,  water,  and 
sulphuric  acid.  The  resulting  product  is  redistilled  with 
calcium  chloride. 

Ethyl  bromide  is  a  very  volatile,  colorless  liquid,  of 
ethereal  odor,  strong,  sweetish,  pungent  taste.  It  is 
heavier  than  water,  and  but  slightly  soluble  in  it;  soluble 


ORGANIC   CHEMISTRY.  281 

in  ether  and  in  alcohol.  It  often  contains  bromoform  as 
an  impurity,  and,  if  it  acquires  a  disagreeable  odor,  be- 
comes brown  on  standing,  or  is  inflammable  or  explosive, 
it  is  not  fit  for  use. 

Use  in  dentistry:  ethyl  bromide  is  a7i  ancEsthetic,  producing 
complete  anaesthesia  in  a  few  minutes,  followed  by  re- 
covery of  consciousness  in  from  one  to  two  minutes  after 
it  is  withdrawn. 

Toxicology:  several  deaths  from  its  use  as  an  anaes- 
thetic were  reported  some  time  ago,  and  its  use  was  dis- 
continued. But  of  late,  according  to  Asch  of  Berlin, 
the  discovery  has  been  made  that  the  toxic  effects  were 
due  to  sulphur  and  arsenic  impurities  consequent  on  the 
old  method  of  preparation,  ft  is  said  that  C.  P.  ethyl  bro- 
mide, made  by  the  modern  method  described  above,  has 
been  used  repeatedly  without  deleterious  results. 

403.  CompoiiiicI  ethers.— Ethyl  nitrite,  CoHsNOg, 
diluted    with   alcohol  forms  "sweet   spirits  of  nitre." 

Amy]  nitrite:  this  substance  is  the  nitrite  of  the  radi- 
cal amyl ;  its  formula  is  CsHuNO.,.*  Molecular  weight, 
117.  It  is  made  by  heating  equal  volumes  of  purified 
amyl  alcohol  (fusel  oil)  and  nitric  acid,  until  the  mixture 
boils.  //  is  a  yellozvish,  ctJicrcal  liquid,  Jiaving  the  odor  of 
over-ripe  pears,  and  an  aromatic  taste.  Its  specific  gravity  is 
from  0.877  to  0.900.  It  is  volatile  and  inflammable,  soluble 
in  alcohol;  solution  rapidly  deteriorates.  Several  samp- 
les of  amyl  nitrite  examined  by  Allen  contained  only  8o 
per  cent,  of  real  amyl  nitrite.  It  is  used  in  dentistry  as 
an  antidote  for  chloroform,  being  administered  by  inhala- 
tion, and  for  relief  of  neuralgia,  epileptic  attacks  during 
extraction  of  teeth,  etc.,  etc. 

Toxicology:  in  administering  amyl  nitrite  by  inhalation. 


*It  may  be  obtained  put  up  in  glass  bulbs  holding  a  drop  or  two. 
The  latter  are  to  be  crushed  before  inhalation. 


282  DENTAL   CHEMISTRY. 

care  should  be  observed.  The  handkerchief  should  be 
withdrawn  when  the  face  becomes  flushed  and  the  heart 
excited. 

404.  Glucosides:  these  bodies  are  regarded 
as  ethers  of  gkicose.*  Those  used  in  dentistry 
are  tannin  and  galHc  acid. 

Tannin,  tannic  acid,  gallotannic  acid,  is 
CuHioOg.  The  tannic  acid  used  in  dentistry 
is  obtained  from  powdered  galls.  It  forms 
light-yellow,  amorphous  scales,  of  faint  char- 
acteristic odor,  and  strongly  astringent  taste, 
easily  soluble  in  water  and  in  dilute  acids. 
Tannin  unites  with  albumin,  gelatin,  etc.,  form- 
ing insoluble  compounds.  In  the  blood,  it 
absorbs  oxygen  and  becomes  gallic  acid.  It 
is  an  active  astringent  and  styptic,  and  is  a 
valuable  agent  in  dentistry  as  a  local  appli- 
cation in  many  disorders,  as  mercurial  stom- 
atitis, hemorrhage  after  extraction,  etc.  It  is 
sometimes  used  dissolved  in  glycerine,  Glycer- 
ituni  Acidi  Tannici,  and  also  in  the  prepara- 
tion known  as  styptic  colloid,  which  is  a  satur- 
ated solution  of  tannin  and  gun  cotton. 

405.  Gallic  acid,  HQH5O5,  or  C6H2(HO)3C02H,  is  ob- 
tained by  exposing  moistened  galls  to  the  air  for  six 
weeks.     A  peculiar  kind  of  fermentation  takes  place,  and 


*  Because  when  treated  by  ferments  or  dilute  acids  they  are  de- 
composed and  yield  glucose  among  other  products.  They  occur  in 
plants,  andare  often  accompanied  by  an  albuminoid  substance  which 
may  act  as  a  ferment  and  turn  them  into  glucose. 


ORGANIC   CHEMISTRY.  283 

the  tannic  acid  of  the  galls  is  converted  into  gallic  acid. 
Gallic  acid  is  a  white  solid,  occurring  in  long,  silky 
needles.  It  has  an  astringent,  slightly  acid  taste,  and  is 
acid  in  reaction.  It  is  not  readily  soluble  in  cold  water; 
it  is  soluble  in  three  parts  of  boiling  water,  in  alcohol,  and 
in  ether.  It  is  used  in  dentistry  in  form  of  a  gargle,  as 
astringent,  antiseptic,  and  styptic. 

406.  Fats  and  fixed  oils:  these  substances,  as  has  been 
stated  before,  are  compound  ethers  of  glyceryl.  Some 
are  liquid  and  others  solid.  Stearin  is  the  constituent  of 
the  more  soWd  idls,  palmitm  of  mutton,  lard,  and  human 
fat;  olcin  is  the  fluid  constituent  of  fats  and  oils;  fats 
treated  with  hot  alkalies  or  with  superheated  steam,  are 
saponified,  as  the  term  is,  stearates,  palmitates,  and 
oleates  of  the  alkalies  being  formed  (soap)  and  gly- 
cerine. 

407.  Cacao  butter  is  a  concrete  oil  from  the  kernels  of 
the  fruit  of  Theobroma  Cacao. 

408.  Waxes  belong  to  the  spermaceti  group  of  oils. 
They  do  not  yield  glycerine  when  saponified. 

409.  Bees-wax  is  the  material  of  which  the  honey- 
comb of  bees  is  composed.  It  occurs  as  a  compact, 
tough,  solid  substance  of  a  yellow  or  brown  color,  almost 
tasteless,  but  of  characteristic,  aromatic  odor.  It  is  not 
greasy  to  the  touch.  On  exposure  to  air  in  thin  slices,  it 
becomes  decolorized.  It  may  be  bleached  by  nitric  acid. 
It  is  insoluble  in  water,  but  soluble  in  the  fixed  oils,  oil  of 
turpentine,  benzol,  ether,  and  carbon  disulphide.  It  is 
difficultly  soluble  in  alcohol.  Its  specific  gravity  is  from 
0.959  to  0.969. 

410.  The  yellow  wax  is  Cera  Flava;  bleached,  it  is 
called  Cera  Alba,  or  white  wax.  The  best  method  of 
bleaching  is  exposure  to  moisture  and  the  rays  of  the 
sun.     A  new  process  is,  first,  to   melt  together  8  parts  of 


284  DENTAL   CHEMISTRY. 

yellow  wax  and  i  to  i)^  parts  of  rectified  oil  of  turpen- 
tine, and  then  expose  to  air,  etc.  Grain  wax  may  be 
bleached  by  dioxide  of  hydrogen.  Other  chemicals  can 
not  be  used  as  they  change  its  constitution. 

411.  Croton  Oil:  this  oil  belongs  to  the  Castor  Oil 
group  of  oils,  distinguished  for  their  very  high  specific 
gravity  and  viscosity.  They  are  readily  soluble  in  alco- 
hol, and  are  strongly  purgative.  Both  castor  oil  and 
croton  oil  are  miscible  with  glacial  acetic  acid  in  all  pro- 
portions. In  drying  character,  they  resemble  the  oils  of 
the  Cotton  Seed  Oil  group. 

It  produces  pustules,  when  applied  to  the  skin,  and  is 
valuable  as  a  counter-irritant. 

Toxicology:  in  overdoses  it  has  frequently  proved 
fatal. 

412.    Chloroform.— 

Synonyms:  trichlormethane,  dichlor-methyl 
chloride,  formyl  terchloride. 

Theoretical  constitution:  CHCI3,  or  methane, 
CH4,  in  which  three  atoms  of  hydro§:en  have 
been  replaced  by  three  of  chlorine.  Chloroform 
has,  in  its  molecule,  one  atom  of  carbon,  one 
of  hydrogen,  and  three  of  chlorine;  by  weight, 
12  parts  carbon,  i  of  hydrogen,  and  106.2  of 
chlorine.     Molecular  weight,  1 19.2, 

Preparation:  commercial  chloroform  is  iisit- 
ally  made  by  the  action  of  bleaching  powder 
on  alcohol;  in  24  parts  of  water  6  parts  of 
bleaching  powder  are  dissolved,  the  mixture 
strained  into  a  retort,  heated  to  i02°F.,  and 
one  part  of  strong  alcohol  added.  The  mix- 
ture is  then  distilled.     Bleaching  powder  is 


ORGANIC   CHEMISTRY.  285 

N  hiefly  calcium  hypochlorite,  which  with  alco- 
hol yields  on  distillation  chloroform,  calcium 
formate,  calcium  chloride,  and  water,  through 
various  intermediate  stages. 

Chloroform  for  anaesthetic  pxivposQs,  purijied 
chloroform,  U.  S.  P.,  is  prepared  from  the 
commercial  by  mixing  with  sulphuric  acid, 
agitating,  drawing  off  the  chloroform,  treating 
with  sodium  carbonate,  and  distilling  over 
calcium  oxide. 

In  a  new  process  for  making  chloroform, 
alcohol  is  said  to  be  dispensed  with,  and  the 
chloroform  made  by  distillation  of  wood  and 
subsequent  treatment  of  the  distillate.  Chlor- 
oform is  also  made  from  chloral  hydrate,  and 
by  electrolysis,  from  chlorides  of  the  alkalies 
in  presence  of  alcohol,  aldehyde,  or  acetone. 

Properties:  chloroform  is  a  v[\o\:>A^,  colorless, 
volatile  liquid  of  bland,  peculiar,  STueetisk, 
ethereal  odor,  and  hot,  aromatic,  saccharine 
taste.  Specific  gravity  of  the  purified  is  i  .5022, 
and  boils  at  I42°F.  The  official  chloroform 
of  the  U.  S.  Pharmacopoea  contains  a  little  alco- 
hol, and  its  sp.  gr.  is  1.488.  It  is  heavier  than 
water  and  not  soluble  in  it,  but  is  freely  soluble 
in  alcohol  and  ether.  //  dissolves  a  large 
number  of  substances,  among  them  camphor, 
fixed  and  volatile  oils,  many  resins,  fats,  caout- 
chouc, sulphur,  phosphorus,  iodine,  bromine, 
and  many  alkaloids. 


286  DENTAL   CHEMISTRY. 

Purified  chloroform  should  not  affect  litmus 
paper,  nor  color  green  a  mixture  of  chromic 
and  sulphuric  acids.  Sulphuric  acid  should 
not  color  it  brown,  nor  should  potassium,  hy- 
drate. Allowed  to  evaporate  on  the  hand,  no 
foreign  odor  should  be  noticed. 

It  is  said  not  to  be  inflammable,  but  is  com- 
bustible burning  with  a  dull,  smoky  flame  on 
application  of  a  naked  flame  to  it. 

Spirit  of  chloroform  contains  an  ounce  of 
chloroform  in  two  ounces  of  dilute  alcohol. 

Uses  in  dentistry:  as  an  ancesthetic,  both  gen- 
eral and  local,  though,  for  the  latter  purpose, 
usually  combined  with  other  agents;  as  an 
anodyne,  and  antispasmodic.  It  is  also  an 
antiseptic  and  styptic.  Applied  to  the  .skin,  it 
acts  as  an  irritant  and  vesicant,  if  evaporation 
is  retarded. 

Toxicology :  deaths  following  administration 
of  chloroform  have  been  quite  frequent.  Pa- 
ralysis of  the  heart,  and,  in  some  cases,  exclu- 
sion of  air  from  the  lungs  are  the  causes  of 
death.  In  administering  it,  some  air  should  be 
admitted  along  with  it.  It  should  never  be 
administered  to  persons  suffering  from  diseases 
of  the  heart  or  kidneys.  At  the  slightest  symp- 
tom of  heart  failure  during  administration  of 
chloroform,  the  patient  should  be  placed  in  a 
recumbent  position,  cold  affusions  applied,  and 
artificial    respiration,   together    with    induced 


ORGANIC   CHEMISTRY.  287 

electricity,  be  resorted  to.  Inhalations  of  from 
three  to  five  drops  of  amyl  nitrite  have  been 
recommended. 

413.  Iodoform:  this  substance,  CHI3,  is 
similar  in  theoretical  constitution  to  chloro- 
form, except  that  it  contains  iodine  instead  of 
chlorine.  It  may  be  made  by  acting;  on  alco- 
hol, aldehyde,  and  many  other  substances 
with  iodine  and  potassium  carbonate  or  hy- 
drate. //  is  71  sit  ally  prepared  by  heating  to- 
gether an  aqueous  solution  of  potassium  car- 
bonate, iodine,  and  alcohol,  until  the  brown 
color  of  the  iodine  has  disappeared.  It  occurs 
in  small,  lemon-yellow,  lustrous  crystals  of  an 
odor^'  not  so  bad  at  first,  but  soon  becoming 
tmsupportable.  It  melts  at  248°F.,  and  vola- 
tilizes g^radually  at  ordinary  temperatures.  // 
is  nearly  insoluble  in  water  and  in  acids,  but 
soluble  in  alcohol,  ether,  chloroform,  disulph- 
ide  of  carbon,  fixed  and  volatile  oils.  It  is  not, 
however,  so  easy  to  dissolve  it,  as  many  of  the 
books  would  lead  us  to  infer.  It  is  neutral  in 
reaction.  Iodoform  is  not  an  escharotic,  and 
is  an  antiseptic,  disinfectant,  and  ancesthetic. 
It  is  now  made  by  electrolysis  from  iodide  of 
potassium  dissolved  in  alcohol,  through  which 
a  stream  of  carbonic  acid  is  constantly  passed. 
Iodoform  is  decomposed  by  sunlig-ht  (turning 

*  The  odor  is  called  "5a^/'cw-///Cv,"  and  is  not  perceptible  in  the 
preparation  known  as  bituminized  iodoform. 


238  DENTAL   CHEMISTRY. 

violet).  It  loses  0.016  per  cent,  an  hour,  ex- 
posed in  a  thin  layer  to  the  air. 

Use  in  dentistry:  it  is  used  as  an  antisef>iic^ 
and  anodyne;  dissolved  in  oil  of  turpentine,  it 
is  said  to  be  a  g:ermicide.  It  acts  chemically, 
by  allowing"  escape  of  free  iodine,  and  also 
mechanically,  favoring-  cicatrization.  In  dent- 
istry, iodoform  is  combined  with  numerous 
agents,  among  them  eucalyptol,  arsenic,  crea- 
sote,  carbolic  acid,  camphor,  etc.,  etc. 

The  odor  of  iodoform  may  be  disguised  by 
mixing-  i  part  of  cumarin  with  25  of  iodoform."^ 
The  odor  may  be  removed  from  the  hands,  by 
washing;  them  in  an  aqueous  solution  of  tannic 
acid.  A  French  antiseptic  dressing  containing- 
iodoform  is  composed  of  equal  parts  of  pow- 
dered iodoform,  cinchona,  benzoin,  and  mag 
nesium  carbonate,  the  latter  being  saturated 
with  eucalyptol.  Acetate  of  potassium  should 
be  given  in  cases  of  poisoning. 

414.  lodol:  tetra-lodo-pyrrhol,  C4I4NH,  made  from 
pyrrole,  a  product  of  the  destructive  distillation  of  pro- 
teids.  Light-yellowish-gray,  micro-crystalline  powder, 
odorless,  almost  tasteless,  almost  insoluble  in  zvater,  soluble 
in  three  parts  alcoholf  (by  weight),  in  2  parts  ether,  and 
in  7  parts  warm  oil.     Contains  nearly  8g  per  cent,  iodine,  and 

*  Oil  of  sassafras  is  also  said  to  be  useful  in  disguising  the  odor. 


t  Alcohol  must  not  be  boiled  when  used  as  a  solvent  for  fear  of 
decomposing  the  iodol. 


ORGANIC   CHEMISTRY.  289 

used  as  a  substitute  for  iodoform.  Used  in  dentistry  as  an 
antiseptic.  lodol  %vax  has  been  used  as  a  temporary  stop- 
ping.    Said  not  to  be  so  toxic  as  iodoform. 

415.  Aldehydes:  aldehydes  lie  midway  be- 
tween alcohols  and  organic  acids;  they  have 
two  less  atoms  of  hydrogen  than  the  corres- 
ponding; alcohol. 

Paraldehyde  (QH3HO)3  or  CgHivOs,  is  used  as  a  sub- 
stitute for  morphine,  and  is  a  liquid. 

416.  Chloral  hydrate. — 

Chloral  is  p4-epared  by  passing  dry  chlorine  into  abso- 
lute alcohol,  until  saturated,  then  adding  sulphuric  acid 
and  distilling.  The  chloral  thus  obtained  is  a  colorless 
liquid;  if,  now,  this  liquid  be  treated  with  a  small  quantity 
of  water,  it  becomes  a  solid,  C2CI3  HO.HgO,  which  is  the 
well-known  chloral  hydrate.  The  latter  is  a  colorless, 
transparent,  crystalline  solid,  of  aromatic,  pungent  odor 
and  taste,  soluble  in  water,  very  soluble  in  alcohol,  ether, 
glycerine,  fixed  and  volatile  oils,  neutral  in  reaction,  melt 
ing  at  I36.4°F.,  and  boiling  at  203'*.  It  has  a  bitter,  caustic 
taste;  it  liquefies  when  mixed  with  carbolic  acid  or 
camphor.  It  volatilizes  slowly  at  ordinary  temperatures. 
It  is  decomposed  by  weak  alkalies  into  chloroform,  and  a 
formate  of  the  alkali  metal;  this  change  was  thought  to 
take  place  in  the  blood  when  chloral  was  taken  internally, 
but  recent  investigations  fail  to  support  the  theory. 

In  preparing  chloral,  5  per  cent,  of  ferric  chloride  is 
added  by  some  to  the  alcohol,  before  the  chlorine  gas  is 
introduced. 

Use  in  dentistry:  chloral  hydrate  is  used  in  dentistry 
locally,  for  relief  of  odontalgia,  etc.  It  is  an  antiseptic, 
and  local  anaesthetic,  especially  when  combined  with 
other  agents.  Chloral  hydrate  is  familiarly  termed 
"chloral." 


290  DENTAL   CHEMISTRY. 

Toxicology:  the  treatment,  in  cases  of  poisoning,  con- 
sists of  use  of  the  stomach  pump,  and  maintenance  of 
respiration. 

417.  Croton-chloral  hydrate  is,  chemically  speaking, 
butyl-chloral  hydrate.  Its.  formula  is  CjHsCljO.HaO.  It  is 
made  by  passing  dry  chlorine  through  aldehyde  cooled 
to  I4°F.  Butyl-chloral  is  obtained,  and,  on  addition  of 
water,  butyl-chloral-hydrate.  It  occurs  in  the  form  of 
crystalline,  micaceous  scales,  of  pungent  odor,  sparingly 
soluble  in  water,  readily  in  alcohol,  and  in  hot  water, 
nearly  insoluble  in  chloroform. 

418.  Ketones:  these  substances  are  con- 
sequent on  the  first  action  of  oxidizing;  agents 
on  secondary  alcohols,  just  as  primary  alcohols 
yield  aldehyde  when  oxidized.  Secondary  al- 
cohols contain  the  g"roup  of  atoms  CHHO,  in- 
stead of  CH2HO,  which  is  found  in  ordinary 
alcohol. 

419.  Organic  acids  and  salts. — 

Organic  acids  may  be  deemed  to  be  built 
upon  the  water  type,  half  the  hydrogen,  in  one 
or  more  molecules  of  water,  being  replaced  by 
a  compound  organic  radical,  always  containing 
oxygen;  for  example,  water  is  H2O  or  H — O — 
H;  replace  half  the  hydrogen,  that  is,  one 
atom,  by  C2H3O,  a  compound  organic  radical 
containing  oxygen,  and  we  have  H—O — C2H3 
O  or  HC2H3O2,  acetic  acid.  It  will  be  noticed 
that  this  formula  is  the  same  as  that  of  ethyl 
aldehyde,  plus  one  atom  of  oxygen.  Alcohol, 
aldehyde,  and  acetic  acid  resemble  one  an- 


ORGANIC   CHEMISTRY.  291 

other  in  a  certain  way.  Thus,  the  formula  for 
ethyl  alcohol  is  CsHeO,  that  of  aldehyde,  C.2H4 
O — or  alcohol  minus  two  atoms  of  hydrog^en — 
and  that  of  acetic  acid,  C0H4O2,  or  aldehyde 
plus  one  atom  of  oxygen. 

420.  Acetic  acid:  its  formula  is  C2H4O2,  or  C0H3O— O 
— H.  It  is  a  monobasic  acid,  like  nitric,  hence  its  formula 
is  conveniently  written,  HQHsO,,  and  the  radical  C.HsOj 
occurs  in  all  acetates,  the  H  (one  atom)  being  replaced 
by  some  positive  element,  as  K,  Na,  Pb,  etc.  Acetic 
acid  is  the  result  of  the  fermentation  of  saccharine  fluids, 
^//rr  alcoholic  fermentation  is  over.  It  is  prepared,  how- 
ever, from  the  rcsidiiary  liquid  obtained  in  the  distillation 
of  wood. 

Aciditm  Accticuvi,  U.  S.  P.,  HC-.-HsO^  =  60,  is  a  watery 
solution,  composed  of  36  per  cent  of  hydrogen  acetate, 
and  64  of  water.  It  is  a  clear,  colorless  liquid,  of  a  dis- 
tinctly vinegar-like  odor,  a  purely  acid  taste,  and  a  strongly 
acid  reaction.  Sp.  gr.  1.048  at  59°F.  Miscible  in  all  pro- 
portions with  water  and  alcohol,  and  wholly  volatilized 
by  heat.  Acidiivi  Aceticitm  Diliitum  has  6  per  cent,  of  ab- 
solute acetic  arid,  and  a  sp.  gr.  of  1.0083.  Acidum  Aceti- 
cwn  Glaciale,  glacial  acetic  acid,  is  nearly  or  quite  abso- 
lute acetic  acid:  at  or  below  59°F.,  it  is  a  crystalline  solid; 
at  higher  temperatures,  a  colorless  liquid.  It  is  very  cor- 
rosive. 

Acetic  acid  dissolves  resins,  camphor,  fibrin,  and  coagu- 
lated albumin;  it  precipitates  mucin.  It  blisters  the  skin 
and  is  a  corrosive  poison:  antidotes  are  alkalies,  alkaline 
carbonates,  soap,  etc.  Glacial  acetic  acid  is  used  by 
dentists,  externally,  as  a  caustic. 

421.  Acetates:  important  acetates  are  those  of  ammo- 
nium, aluminium,  and  lead. 

Spirit  of  Miiidererus:  ammonium  acetate,  NHi(C2H3 


292  DENTAL   CHEMISTRY. 

O2).  To  make  it,  saturate  dilute  acetic  acid  with  ammo- 
nium carbonate  and  filter.  Colorless,  pungent,  odorless 
liquid;  should  be  freshly  made. 

Used  in  dentistry  as  a  lotion,  and  internally  as  a  refrig- 
erant. Its  formula  is  usually  written  NH4C2H3O2.  It  is 
completely  volatilized  by  heat. 

422.  Aluminium  acetate:  a  solution  of  it,  known  as 
Liquor  Aluminii  Acetatis,  occurs  in  pharmacy  and  is  used 
by  dentists  as  an  antiseptic,  disinfectant,  and  deodorizer. 
It  contains  from  7^  to  8  per  cent  of  basic  aluminium 
acetate.     (AUHOMQHjOO.,  324)- 

423.  Lead  acetate  is  known  officially  as  Plumbi  Acetas, 
Pb  (C2H:;02)2,  3H2O  =  378.5.  For  pharmaceutical  pur- 
poses it  is  made  from  oxide  of  lead,  acetic  acid,  and 
water;  PbO  +  2HCH3O2  +  2H,0  =  Pb(C2H30,),3H20 
Colorless,  glistening,  transparent  crystals,  efflorescent, 
soluble,  of  sweetish,  astringent  taste.  Aqueous  solutions 
become  turbid  from  presence  of  carbon  dioxide  of  the 
air,  causing  formation  of  carbonate  of  lead  which  is  insol- 
uble. 

424.  Sub-acetate  of  lead :  the  acetate  and  hydrate, 
basic  acetate,  Pb(C2H302)2,  Pb(HO).,.  Colorless  liquid, 
more  poisonous  than  the  acetate.  Precipitated  by  solu- 
tions of  gum.  Used  in  Goulard's  extract.  Liquor  Plumbi 
Subacetatis,  a  25  per  cent,  solution  of  the  sub-acetate. 

425.  Lead  water,  which  is  two  fluidrachms  of  Liquor 
Plumbi  Subacetatis  in  a  pint  of  distilled  water,  is  used  in 
dental  practice  as  a  local  application.  It  is  known  as 
Liquor  Plumbi  Subacetatis  Dilutus. 

Compounds  of  lead  are  poisonous,  but  chronic  poisoning 
is  more  common  than  acute;  in  the  latter  case,  emetics 
should  be  administered  or  the  stomach  pump  used,  large 
draughts  of  milk  containing  white  of  q^^  giv'en,  and  sul- 
phate of  magnesium  dissolved  in  dilute  sulphuric  acid. 

426.  Trichloracetic  acid  should  really  be  considered 


ORGANIC   CHEMISTRY.  293 

under  the  head  of  chloral  hydrate,  for  it  is  formed  when 
the  latter  is  oxidized  by  nitric  acid.  It  is  called  also  tri- 
chloroacetic acid.  Its  formula  is  HC4CI3O2;  it  is  a  colorless, 
crystalline  solid,  soluble  in  water  and  in  alcohol.  It  is  a 
caustic  and  coagulates  albumin.  It  is  used  in  dentistry 
as  a  germicide  and  an  antiseptic.  According  to  Dr.  Filip- 
powitch  it  is  a  powerful  antiseptic  even  in  0.2  per  cent, 
solutions,  while  in  i  per  cent,  or  2  per  cent,  solutions  it 
destroys  all  forms  of  organic  life;  in  5  per  cent,  it  does 
not  arrest  the  growth  of  yeast,  but  does  that  of  bacteria 
and  micrococci. 

427,  Benzoic  acid:  formula,  HC7H5O2.  This  acid  may 
be  obtained  from  benzoin,  naphthalin,  toluol,  or  from  the 
urine  of  herbivorous  animals.  It  is  a  solid  substance  oc- 
curring in  lustrous  blades,  or  needles,  but  slightly  soluble 
in  cold  water,  soluble  in  boiling  water,  more  soluble  in 
alcohol  and  ether.  Borax  added  to  it  increases  its  solu- 
bility in  water,  as  does  sodium  phosphate  also.  The  acid 
is  monobasic,  like  nitric  acid.  Most  benzoates  are  solu- 
ble. Benzoic  acid  is  an  antiseptic,  and  is  used  in  dentistry 
as  such;  also,  as  a  local  haemostatic,  in  combination  with 
powdered  alum.  It  is  one  of  the  ingredients  of  Harris's 
Gum  Wash. 

Ainmonium  bensoate ,  NH^CrHsOa  =  139,  is  the  benzoate 
most  used.  It  occurs  in  the  form  of  prismatic  crystals, 
colorless,  and  transparent,  or  white  and  granular,  soluble 
in  5  parts  of  water.  It  becomes  yellow  on  long  exposure 
to  air.  Benzoates,  like  benzoic  acid,  are  antifermentative 
in  action.  Ammonium  benzoate  is  administered  in  cases 
of  phosphatic  calculus,  which,  in  time,  it  dissolves.  Lith- 
iiun  benzoate  has  for  its  formula  LiC^HjOa  =  128.* 

*  A  derivative  of  benzoic  acid  is  the  new  sweet  substance  Sac- 
charin ;  a  white,  crystalline  powder,  soluble  in  250  parts  water, 
easily  soluble  in  alcohol  and  ether.  Said  to  be  280  times  as  sweet  as 
cane-sugar.     Solubility  increased  by  addition  of  alkaline  solutions. 


294 


DENTAL    CHEMISTRY. 


428.  Eugenic  acid. — 

Synonyms:  eugenol,  caryophyllic  acid,  oxidized  es- 
sence of  cloves. 

Theoretical  constitution:  CioHi/).,. 

Occurrence:  found  along  with  a  hydrocarbon  in  oil  of 
cloves. 

Preparation:  crude  oil  of  cloves  treated  with  potash  is 
distilled,  and  the  residue  is  subjected  to  the  action  of  a 
mineral  acid.  The  substance  may  also  be  obtained  from 
cinnamon  leaves. 

Properties:  colorless  oil  of  sp.gr.,  1.07,  of  spicy,  burning 
taste,  soluble  in  water  and  in  alcohol.  Reddens  litmus, 
and  coagulates  albumin.  On  contact  with  air,  becomes 
darker  and  resinous. 

Use  in  dentistry:  as  a  germicide,  obtunding  agent,  etc., 
etc.  • 

429.  JFydrocyanic    acid:     Acidum     Hydrocyanicum, 

HCN  or  HCy,  cyanhydric  acid.  Exists  ready  formed  in 
juice  of  the  bitter  cassava;  may  be  obtained  from  bitter 
almonds,  kernels  of  plums  and  peaches,  apple  seeds, 
cherry  laurel,  etc.;  clear,  colorless,  volatile  liquid,  of 
peculiar,  pungent  odor.  The  official  acid  contains  about 
2  per  cent,  of  the  anhydrous  acid.  Its  compounds  are 
cyanides,  or  cyamirets,  as  formerly  termed. 

430.  Mercuric  cyanide,  HgCy  or  HgCN,  has  already 

been  considered. 

431.  Oleic   acid:     formula   CisHsiOa,  or  HCiglissOj,  or 

CjvHssCOOH,  is  of  the  fatty  acid  series,  like  acetic  acid. 
It  is  found,  in  combination  with  glyceryl,  in  most  animal 
fats  and  non-drying  vegetable  oils.  Its  salts  are  called 
olcatcs,  and  are  definite  chemical  compounds. 

Metallic  oleates  seem  to  e.xert  an  antiseptic  action,  not 
only  on  the  fats  with  which  they  may  be  combined,  but 
also  on  discharges  from  suppurating  surfaces,  etc.,  etc. 
The  pure  oleic  acid   is  free  from   unpleasant  odor  or  ran- 


ORGANIC    CHEMISTRY.  295 

cidit}-.  Oleates  of  the  alkaloids  are  prepared  by  dis- 
solving the  alkaloid  in  oleic  acid.  Important  oleates  are 
those  of  aluminium,  arsenic,  bismuth,  cadmium,  copper, 
iron,  lead,  mercury,  silver,  tin,  zinc,  and  iron. 

432.  Mercuric  oleate  is  of  stable  composition,  as  now 
prepared,  and  has  all  the  therapeutic  effects  of  mercury. 
It  does  not  become  rancid  nor  stain  the  linen.  Its  formula 
is  Hg(Ci8H3302)2  "-  762.  It  is  made  from  yellow  mercuric 
oxide.     The  official  U.  S.  P.  oleate  is  a  liquid. 

Percentage  of  Metal  in  the  Metallic  Oleates. 

100  parts  of  oleate  of  correspond  to  Oxide  % 

Aluminium AL^Oj  5.86 

Arsenic As-^Os  21.55 

Bismuth BijOa  22.22 

Copper CuO  12.67 

I ron  ( ferric ) Fe.Os  8.89 

Lead PbO  28.95 

Mercury  (precip.) Hg  28.32 

Silver Ag^O  29.77 

Zinc ZnO  12.90 

433.  Oxalic  acid:  H-XC^Ot),  2H2O  =  126. 

Occurs  in  combination  in  Oxalis  and  in  Rhubarb. 
Made  from  sawdust  by  action  of  caustic  alkali.  Color- 
less-, transparent  crystals,  readily  soluble,  odorless,  of 
intensely  acid  taste.     Dangerous  poison. 

The  treatment,  in  cases  of  poisoning,  consists  in  giving 
lime,  chalk,  or  magnesia  in  very  small  quantities  of  milk, 
and  subsequently  emetics  if  there  is  no  vomiting. 

434.  The  salts  of  oxalic  acid  are  oxalates,  and  con- 
tain CoOii  the  acid  '  is  dibasic,  hence  calcium  oxalate 
w'ould  have  CaC^O^  for  its  formula;  potassium  oxalate, 
KjCjOi,  etc.,  etc. 

435.  Cerium  oxalate  is  Ce2(Co04)3.9H20  =  708. 

436.  Lactic  acid:  this  acid  is  of  importance 


290  DENTAL    CHEMISTRY. 

to  the  dental  student  in  view  of  the  experi- 
ments of  Miller,  Black,  Mag^itot,  and  others  in 
reg"ard  to  caries. 
Theoretical  constitution:  CsHeOs 

CHa 

I 
g-raphically    CH — O — H 

CO.O— H. 

Composed  of  3  atoms  of  carbon,  6  of  hydro- 
gen, and  3  of  oxygen;  by  weight  36  parts  of 
carbon,  6  of  hydrogen,  and  48  of  oxygen. 
Molecular  weight,  90.  Formula  usually  writ- 
ten HC3H5O3,  to  denote  the  monobasic  char- 
acter of  the  acid. 

Occurrence  and  preparation:  lactic  acid  is 
the  acid  of  sour  cabbage  and  of  sour  milk.  It 
is  produced  in  these  substances  by  the  action 
of  a  special  ferment  called  lactic  ferment. 
It  is  found  in  several  parts  of  the  human  body, 
namely,  in  the  urine,  intestinal  juices,  and ,  in 
the  gastric  juice.  It  exists  in  many  products 
after  fermentation,  as  in  beet  juice,  various 
vegetables,  nux  vomica. 

437.  It,  or  isomeric  modifications  of  it,  oc- 
curs in  the  fluids  which  permeate  muscular 
tissues.  A  variety  called  sarco-lactic  acid  is 
found  in  the  muscles  and  also  in  the  hepatic 
cells.  Abiioriually,  lactic  acid  is  found  in  the 
blood,  particularly  in  leukaemia,  pyaemia,  etc.; 


ORGANIC   CHEMISTRY.  297 

it  may  be  found  in  purulent  discharges,  in  the 
saHva  in  diabetes,  and  in  the  urine,  especially 
after  phosphorus  poisoning,  in  acute  atrophy 
of  the  liver,  leukaemia,  trichinosis,  and  occal 
sionally  in  rickets  and  osteomalacia. 

438.  On  a  large  scale  lactic  acid  is  prepared  by  the 
lactic  fermentation,  so  called,  of  cane  sugar  and  glucose. 
Flour  is  treated  with  dilute  sulphuric  acid  and  its  starch 
thus  converted  into  glucose;  the  free  sulphuric  acid  is 
neutralized  with  milk  of  lime  and  sour  milk  is  added, 
which  gives  rise  to  a  fermentation  in  the  sugars.  This 
fermentation  is  checked  before  the  so-called  butyric  fer- 
mentation sets  in,  by  heating  to  the  boiling  point.  Cal- 
cium lactate  is  formed,  and  the  hot  solution,  after  filtra 
tion,  is  evaporated  down  and  allowed  to  crystallize. 
From  calciumlactate,  lactic  acid  is  obtained  by  saturation 
with  sulphuric  acid. 

In  the  human  body,  lactic  acid  is  possibly  a  derivative 
of  sugar: 

CcH,A.  =  2(QH603) 

Glucose.  Lactic  acid. 

It  is  decomposed  in  the  system  into  carbonic  acid  and 
water,  perhaps  splitting  up  first  into  butyric  acid,  carbonic 
acid,  and  hydrogen. 

The  lactic  acid  found  in  sour  milk  is  produced  by  the 
transformation  of  the  sugar  of  milk  into  lactic  acid,  by  the 
influence  of  decomposing  casein: 

C,2He,0„        +         H,0 '       =        4HC3H5O3. 

Milk-sugar.  Water. 

Properties:  the  official  U.  S.  P.  lactic  acid  is  a  color- 
less, syrupy,  odorless,  strongly  acid  liquid  containing 
75  per  cent,  of  lactic  acid.  Sp.  gr.,  1.212.  It  mixes 
readily  with  water,  alcohol,  and  ether;  is  nearly  insoluble 
in  chloroform. 


298  DENTAL   CHEMISTRY. 

Lactic  acid  possesses  the  property  of  dis- 
solving" calcium  phosphate.  It  has  been 
shown,  by  Magitot  and  others,  to  be  capable 
of  decomposing-  the  teeth;  sections  of  dentine, 
placed  by  Miller  in  infected  culture  fluids, 
were  decomposed  by  the  lactic  acid  formed. 
Leber  and  Rottenstein  found  that  solutions  of 
lactic  acid,  i  part  in  lOO  of  water,  decalcified 
the  teeth. 

Miller's  experiments  tend  to  show  that, 
during  caries,  lactic  acid  is  formed  in  the 
teeth  and  in  sufficient  amount  to  destroy  the 
dentine. 

439.  Lactic  acid  is  a  monobasic  acid,  HfCuH-.O:!); 
its  salts  are  lactates,  and  are  all  soluble.  Phosphates  dis- 
solved in  lactic  acid  form  lacto-phosphates.  Calcium  lacto- 
phosphate  is  made  by  the  action  of  lactic  acid  on  calcium 
phosphate. 

440.  Salicylic  acid:  formula  CiHoOs,  or  HC7H5O3,  or 
C6H4(OH)C02H.  It  is  also  called  oxybenzoic  acid.  It 
forms  a  large  percentage  of  oil  of  vvintergreen,  but  is  pre- 
pared on  a  large  scale  by  the  action  of  carbon  dioxide  on 
sodium  phenate  (carbolate). 

Properties:  odorless,  white  and  lustrous  masses  of  fine, 
small,  colorless  needles,  soluble  in  boiling  water  and  in 
alcohol;  tasteless  at  first,  but  afterwards  sweet  and 
astringent,  causing  acridity  of  the  fauces;  soluble 
in  cold  water  containing  three  parts  of  sodium 
phosphate.  Antiseptic  and  disinfectant.  Heated  dry  in 
a  test  tube,  sublimes  in  beautiful  needles  before  melting- 
point  is  reached,  and  at  higher  temperature  is  dissipated. 
It  is  soluble  in  alcohol,  ether,  and  glycerine.  Its  salts 
are  salicylates;  it  is  a  monobasic  acid,  H(C7H503),  there- 


ORGANIC   CHEMISTRY,  299 

fore,  sodium  salicylate,  for  example,  is  NaCrHgOs.  Sali- 
cylic acid  is  used  in  dentistry  as  an  antiseptic,  dissolved 
in  water  containing  a  little  sodium  phosphate  or  sodium 
sulphite,  or  in  glycerine,  or  in  ether.  It,  like  many  other 
acids,  attacks  the  teeth  slightly,  hence  is,  not  suitable  for 
mouth  washes.     It  is  acid  in  reaction. 

441.  Salol:  this  substance  is  the  phenyl  ether  of  sali- 
cylic acid,  that  is,  phenyl  salicylate,  CgHiOH.COO.CeHj; 
empirically,  C6H5C7H5O,,  one  atom  of  hydrogen  in  salicy- 
lic acid  being  replaced  by  the  univalent  radical  CgHs.  It 
is  a  white  crystalline  powder,  of  mild  aromatic  odor,  in- 
soluble in  water  but  soluble  in  alcohol.  Used  in  dentistry 
as  an  antiseptic. 

Betol  is  the  salicylate  of  beta-naphthol,  CgH.OH.COO. 
C10H7.  Said  to  be  freer  from  detrimental  properties  than 
alcohol,     White,  insoluble  in  water.  '^ 

442.  Sozolic  Acid  (formerly  called  Aseptol*): 
Formula,  C6H4(HO)S02(HO),  orthoxy-phenyl-sulphur- 

ous  acid,  containing  SOo  in  place  of  carbonyl  (CO)  of 
salicylic  acid. 

It  is  a  reddish  syrupy  liquid,  of  sp.  gr.,  1.40,  with  a 
feeble  and  not  disagreeable  odor.  It  dissolves  in  water 
in  all  proportions.  With  ferric  chloride  it  gives  the  same 
violet  coloration  as  salicylic  acid.  Though  a  decided 
acid,  it  has  not  the  corrosive  action  of  phenol.  It  is  said 
to  arrest  absolutely  every  fermentation,  diastatic  or 
fungoid,  to  a  much  greater  degree  than  phenol  and  other 
well-known  antiseptics.  The  advantages' of  sozolic  acid 
lie  chiefly  in  its  great  solubility  and  freedom  from  odor — 
qualities  which,  together  with  the  absence  of  corrosive 
action,  should  make  it  suitable  for  toilet  preparations 
in  many  cases. 

*  Aseptol  is  a  33^  per  cent,  solution  of  the  acid. 


300  DENTAL    CHEMISTRY. 

It  is  a  valuable  antiseptic,  according  to  D.  F.  Hueppe, 
and  doubtless  will  partially  replace  carbolic  acid  as  a  dis- 
infectant and  antiseptic.  It  would  seem  destined  to  be 
of  value  in  dentistry  in  treatment  of  fetor  of  the  breath. 

443.  Tartaric  acid :  H2(C4H40c),  Acidum  Tartaricum. 
Occurs  in  grapes,  pineapples,  tamarinds,  and  other  fruits, 
as  a  tartrate.  Prepared  from  crude  tartar.  Colorless, 
transparent  crystals,  soluble  in  water.  Solutions  are 
strongly  acid,  and  deposit  fungous  growth. 

In  dentistry  it  is  used,  combined  with  "chloride  of 
lime,"  to  bleach  discolored  teeth. 

444.  Cream  of  tartar  or  potassium  bitartrate:  po- 
tassium acid  tartrate,  KH(C4H406),  made  from  argols  or 
crude  tartar,  a  deposit  on  the  sides  of  wine  casks;  odor- 
less, of  gritty  taste,  white,  almost  insoluble  in  cold  water, 
soluble  in  from  15  to  20  parts  boiling. 

445.  Roclielle  salt:  potassium  sodium  tartrate,  KNa 
(OH'Oe)  4H2O.  Large,  transparent,  colorless,  slighth' 
efflorescent  crystals,  of  mildly  saline  and  bitter  taste, 
readily  soluble. 

446.  Tartar  emetic:  tartrate  of  potassium  and  a  radi- 
cal called  stibyl;  potassium  antimonyl  tartrate,  2(KSbO. 
CiHtOfl).!!.^©  =  664,  is  prepared  by  boiling  4  parts  of 
antimonous  oxide  with  5  parts  of  cream  of  tartar  in  50  of 
water.  It  is  soluble  in  17  parts  of  water,  but  insoluble  in 
alcohol.  It  is  poisonous:  treatment  should  consist  in  use 
of  stomach  pump  or  emetics,  administration  of  tannin  in 
form  of  tea,  infusion  of  nut  galls,  oak  bark,  etc.,  and  of 
stimulants. 

447.  Otiier  organic  acids:  valeric  or  valerianic,  HC5 
H9O2;  citric: H3C6H5O7.H2O.  A  new  disinfectant  is  oxy- 
naphthoic  acid,  alpha:  a  white,  odorless,  micro-crystal- 
line powder,  nearly  insoluble  in  water,  soluble  in  alcohol. 


ORGANIC   CHEMISTRY.  301 

ALKALOIDS. 

448.  ilkaloids  are  artificial,  natural,  or 
cadaveric.  Artificial  alkaloids  are  the  various 
amines,  as  methylamine,  ethylamine,  etc. 
Methylamine  is  a  gas,  ethylamine  a  liquid, 
propylamine  a  volatile  oil.'^ 

449.  The  natural  alkaloids:  a  class  of  sub- 
stances chiefly  of  vegetable  origin,  often  active 
principles  of  plants,  supposed  to  be  like  alka- 
lies, hence  name.  Those  containing  no  oxy- 
gen are  volatile;  those  having  oxygen  are  non- 
volatile. As  a  rule,  are  soluble  in  alcohol, 
ether,  chloroform;  contain  nitrogen,  turn  plane 
of  polarized  ray  of  light  to  left  (with  few 
exceptions),  furnish  with  platinic  chloride, 
double  chlorides;  have  bitter  taste,  resemble 
alkalies  in  uniting  with  acids  to  form  salts,  of 
which  the  sulphates,  nitrates,  chlorides,  and 
acetates  are  usually  soluble,  and  the  oxalates, 
tartrates,  and  tannates  usually  insoluble;  in 
solution  are  precipitated  by  many  re-agents, 
including  iodine  dissolved  in  iodide  of  potas- 
sium: very  poisonous. 

The  alkaloids  used  in  dentistry  are  for  the  most  part 
tiatural  alkaloids,  as  morphine,  cocaine,  etc.,  etc. 

Cadaveric  alkaloids,  or  ptoinaincs,  are  those  found  in 
putrefying    animal    or   vegetable    matter,  and,  in    certain 


*  Many  therapeutic  agents  have  been  discovered  among^  the 
amines  and  their  derivatives,  e.  s;.  antifebrin,  a  derivative  of  aniline 
which  is  'UsqM,  phcnylatnine. 


302  DENTAL   CHEMISTRY. 

pathological  conditions,  in  the  human  body  during  life, 
Pyaemic  fluid  yields  an  alkaloid,  which  has  been  named 
septicine. 

Most  of  the  natural  organic  bases  or  alkaloids  resemble 
the  -amines  or  compound  ammonias;  an  -amine  may  be 
regarded  as  formed  by  the  replacement  of  one  or  more 
atoms  in  the  ammonia  (NHj)  molecules  by  positive  or 
hydrocarbon  radicals,  thus: 


N 


ammonia  methylamine. 

Some  of  the  alkaloids  are  more  like  ammonium  com 
pounds  than  like  amines.     The  molecular  structure  of  the 
vegetable   alkaloids  is,  in   most   cases,  but   very  imper- 
fectly understood. 

450.  Aconitiiie:  CsoHiyNO;,  is  the  alkaloid  of  aconite, 
Aconitiwi  Napellus,  occurring  as  a  glacial  mass  or  white 
powder,  crystallizing  with  difficulty  in  rhombic  plates. 
It  is  soluble  in  150  parts  of  water,  slightly  soluble  in  am- 
monia water,  soluble  in  benzol,  soluble  in  2  parts  ether, 
soluble  in  2^^  parts  chloroform.  It  has  a  sharp,  pungent 
taste,  and  is  one  of  the  most  powerful  poisons  known. 
It  is  fatal,  probably,  in  doses  of  /^th  grain.  Samples  of 
aconitine  vary  in  strength,  some  being  wholly  inert,  others 
powerfully  poisonous.  Morson's  and  Duquesnel's  crystal- 
ized  aconitine  have  about  the  same  solubility,  and  are 
of  about  the  same  strength.  Duquesnel's  is  in  form  of 
large  crystals  usually,  some  weighing  lUh  of  a  grain. 

Oleate  of  aconitine  contains  usually  2  per  cent,  of  the  alka- 
loid. 

Aconitine,  in  dental  practice,  is  administered  internally, 
for  neuralgia  of  the  fifth  pair  of  nerves.  The  treatment, 
in  cases  of  poisoning,  should  consist  in  administration  of 
emetics,  and  of  stimulants  as  ammonia,  brandy,  strong 


ORGANIC   CHEMISTRY.  3()3 

coffee,  and  tea.  Liniments  and  friction  to  the  limbs  and 
spine  should  be  used,  mustard  plasters  applied  to  pit  of 
stomach,  and  slight  galvanic  shocks  through  the  heart 
administered. 

Tincture  of  aconite  is  a  valuable  local  application  in 
dentistry,  especially  when  combined  with  various  agents, 
as  iodine,  chloroform,  etc.  Poisoning  by  tincture  of  aco- 
nite is  to  be  treated  as  above;  the  chief  symptoms  are 
numbness  and  tingling,  great  sense  of  fatigue,  muscular 
weakness,  etc.,  etc. 

451.  Napclline,  an  alkaloid  obtained  by  Duquesnel 
from  aconite,  is  less  powerful  than  aconitine,  and  has 
hypnotic  properties. 

452.  Atropine:  CnHjsNOa.  This  alkaloid  is  from 
Atropa  Bellado7ina.  The  sulphate  of  atropine  is  used  in 
dentistry.  Its  formula  is,  (C,7H.j:iNO:j).iH2SOi,  and  it  is 
made  by  combining  atropine  with  sulphuric  acid  and 
evaporating.  [The  hydrogen  of  acids  is  not  replaced  by 
alkaloids,  when  they  combine  with  the  acids;  in  this  re- 
spect the  compounds  formed  differ  from  compounds  of 
the  alkali  metals  and  acids:  thus,  while  atropine  sulphate 
is  (C.rHvsNOs).;,  H0SO4,  potassium  sulphate  is  KoSO^]. 

Atropine  sulphate  is  a  white,  crystalline  powder,  or 
forms  small,  colorless,  silky  prisms.  It  is  soluble  in  3 
parts  cold  water,  and  lO  parts,  90  per  cent  alcohol. 
The  concentrated  solution  should  be  Jieutral  to  test  paper. "^  It 
is  insoluble  in  ether,  inodorous,  of  disagreeable,  bitter 
taste,  and  is  an  active  poison.  In  dental  practice,  it  is 
used  locally  as  an  obtunding  agent,  etc.,  and  also  intern- 
ally, for  neuralgia,  etc.  The  fatal  dose  is  two  grains;  the 
treatment  should  consist  in  administration  of  emetics, 
and  subcutaneous  injection  of  pilocarpine  or  of  morphine. 

*  In  order  to  test  atropine  sulphate,  drop  a  little  of  the  dry  powder 
on  litmus  paper,  both  red  and  blue,  previously  moistened  with 
water.     It  should  not  affect  either  paper. 


304  DENTAL   CHEMISTRY. 

Dryness  of  the  throat,  diplopia,  vertigo,  and  in  serious 
cases,  delirium,  are  among  the  symptoms  of  poisoning  by 
this  substance. 

453.    Chinoline  or  quinoliiie:  C9H7N. 

This  substance  is  an  artificial  alkaloid,!  and  is  not  the 
active  principle  of  any  plant.  It  was  first  made  from  coal 
tar,  then  from  cinchona,  but  now  is  made  from  nitroben- 
zole,  aniline,  and  glycerine,  to  which  sulphuric  acid  has 
been  added,  the  mixture  being  heated  and  cooled  altern- 
ately. It  is  a  colorless,  oily  liquid,  of  sp.  gr.  1.094,  and 
boiling  at  460°  F.  In  chemical  constitution  it  may  be  re- 
garded as  naphthalin,  CioHg,  in  which  one  CH  group  is  re- 
placed by  N. 

Chinoline  forms  crystalline  salts  with  acids.  The  one 
used  in  dentistry  is  the  tartrate,  (C9H7N)2  HaCJIiO,-,, 
theoretically,  but  the  real  composition  of  German  chino- 
line tartrate  is  said  to  be  3C9H7N.4C4H6O6,  requiring  60.8 
per  cent,  of  tartaric  acid.  Chinoline  tartrate  forms 
(microscopic)  columnar  crystals;  it  is  soluble  in  75  parts 
of  water  at  6o.8''F.,  and  in  150  parts  of  go%  alcohol,  and 
350  of  ether.  Its  taste  is  peculiar,  somewhat  burning, 
penetrating,  and  suggesting  peppermint.  It  has  a  faint 
odor,  slightly  suggesting  bitter  almonds. 

It  is  used  in  dentistry  as  an  antiseptic,  usually  in  5 
per  cent,  solution.  It  is  sometimes  combined  with  carbolic 
acid.  Its  aromatic  odor  is  less  pleasant  than  that  of 
pyridine,  which  it  resembles. 

Chinoline  enters  into  a  definite  combination  with  iodo- 
form. One  part  of  iodoform,  dissolved  in  ether,  is  mi.xed 
with  three  of  chinoline  also  dissolved  in  ether. 

Salts  of  chinoline  should  be  kept  away  from  the  light. 


'\ Aniipyrine    is  a  derivative  of  chinoline;  and  is  an  antipyretic 
and  anodyne. 


ORGANIC   CHEMISTRY.  305 

454.  Cannabis  Indica  products:  the  tincture  of  Canna- 
bis Indica,  diluted  3  to  5  times,  has  been  used  by  A. 
Aaronson  and  others,  as  a  local  anaesthetic  in  extracting 
teeth. 

455.  Cannabinum  Tanniciim  or  cannabin  tannate 
occurs  as  an  amorphous,  yellowish  or  brownish- 
gray  powder,  indifferent  toward  litmus,  having  a  very 
faint  odor  of  hemp,  and  a  somewhat  bitter,  strongly 
astringent  taste.  When  heated  on  platinum  foil,  it  swells 
up  and  finally  leaves  minute  traces  of  a  white  ash.  It  is 
almost  insoluble  in  cold  water,  alcohol  or  ether,  and  dis- 
solves but  little  on  warming;  but  it  is  easily  soluble  in 
water  or  alcohol  acidulated  with  hydrochloric  acid. 

456.  Cannabine:*  this  is  the  name  of  an  alkaloid  re- 
cently prepared  from  Cannabis  Indica.  It  appears  as  a  vis- 
cid, brown  substance,  transparent  in  thin  layers,  of  a 
strongly  aromatic  odor  and  a  sharp,  bitter,  and  somewhat 
scratching  taste.  It  is  insoluble  in  water,  easily  soluble  in 
alcohol,  ether,  petroleum  ether,  chloroform,  benzol,  disul- 
phide  of  carbon,  ethereal  and  fixed  oils.  The  solutions  are 
golden-yellow  when  highly  diluted,  brown  when  con- 
centrated. When  heated  on  platinum  foil  it  leaves  no 
residue. 

457.  Cocaine:  CnHsiNO^.  This  now  famous  alkaloid 
is  prepared  from  ErytJiroxylon  Coca,  a  shrub  indigenous  to 
certain  regions  in  South  America.  It  is  found  chiefly  in 
Peru  and  Chili,  and  the  alkaloid  is  extracted  from  the 
leaves.  The  process  of  extracting  cocaine  from  coca 
leaves  is  given  in  full  in  Squibb's  Ephemeris,  Vol.  II.,  No. 
7;  it  is  too  long  for  insertion  here. 

Pure  cocaine  crystallizes  in  colorless,  four  or  six  sided 
monoclinic  prisms,  soluble  in  704  parts  of  water  at 
53.6°F.,  easily  soluble  in  alcohol,  and  still  more  so  in  ether. 

*  The  pure  alkaloid  must  be  carefully  distinguished  from  the  resi- 
noid  called  "Cannabin."' 


306  DENTAL   CHEMISTRY. 

Cocaine  melts  near  197T.  Cocaine  combines  readily  with 
dilute  acids,  forming  easily  crystallizable  salts,  which  are 
more  or  less  sparingly  soluble  in  water,  but  soluble  in 
alcohol.  They  are  insoluble  in  ether,  of  bitter  taste,  and 
leave  a  transient  sensation  of  insensibility  upon  the 
tongue. 

The  hydroehlorate,  or  muriate,  of  cocaine  is  the  salt 
which  has  been  most  used.  The  crystallized  hydroehlorate 
has  for  its  formula,  Ci7HziNOt,HCL  2H20,  when  crystal- 
lized from  aqueous  solutions.  Dried  and  rendered  anhy- 
drous, its  formula  is  CnHgiNOi.HCl.;  crystallized  from 
alcohol  (B.P.),  its  formula  is  the  same  as  the  latter,  for  it 
is  anhydrous.  Hydroehlorate  of  cocaine  occurs  in  the 
form  of  short,  transparent,  prismatic  crystals,  permanent 
in  air.  It  is  sparingly  soluble  in  water,  but  readily  solu- 
ble in  alcohol,  ether,  and  in  vaseline. 

The  hydroehlorate  is  termed  hydrochloride  by  some 
authors;  the  hydrogen  of  the  hydrochloric  acid  is  not 
given  off  in  the  combination,  as  is  seen  from  the  formula. 

458.  Other  compounds  of  cocaine  are  the  hydrobromate, 
C„H2iNO„HBr;  the  citrate,  (CnHaiNOOsHsCeHsO,;  the 
oleate,  (CnH2iN04)HCi8H3302,  containing  5  per  cent,  of 
the  alkaloid;  the  salicylate,  C17H21NO4,  HC7H5O3,  the 
phenate  or  carbolate*,  and  the  phtalate.  Salts  of 
cocaine  are  used  in  dentistry  as  local  anaesthetics  and  ano- 
dynes, especially  in  alveolar  pyorrhoea,  extirpation  of 
pulps  of  teeth,  and  that  of  hypersensitive  dentine.  They 
have  also  b^cn  used  by  injection,  for  extraction  of  teeth. 
Combined  with  menthol,  and  dissolved  in  alcohol,  chloro- 
form, or  ethyl  bromide,  they  are  used  as  a  lotion  in  neu- 
ralgia and  odontalgia;  for  the  same  purpose,  dissolved  in 
oil  of  cloves.     Toxic   symptoms  have   followed  injection 


*  The  carbolate  is  a  colorless  mass  of  faint  odor,  very  readily  solu- 
ble in  alcohol. 


ORGANIC   CHEMISTRY.  gQ" 

of  6  drops  of  a  20  per  cent,  solution  into  the  gums;  re- 
lieved by  inhalation  of  amyl  nitrite,  3  drops  at  a  time,  3 
inhalations. 

Th.Q  purity  of  cocaine  salts  is  of  the  greatest  importance. 
The  permanganate  test  should  be  used  for  possible  or- 
ganic impurities.* 

459.  Morphine:  morphine,  morphia,  CnHisNOs.H-jO, 
exists  as  meconate  of  morphine  in  opium,  which  is  the 
concrete,  milky  juice  exuding  on  incising  the  unripe  cap- 
sules of  Papavcr  Somniferum,  or  white  poppy.  On  account 
of  the  comparative  insolubility  of  morphine,  its  salts  are 
preferred  for  use  in  dentistry.  Of  these  the  acetate, 
hydrochlorate,  and  sulphate  are  ofificial.  They  are  all 
freely  soluble  in  water. 

460.  Morphine  acetate,  (CnHi9N03)HQH302.3H20,  oc- 
curs in  the  form  of  a  white  or  yellowish  white,  amorphous 
or  crystalline  powder  of  bitter  taste.  Soluble  in  both 
alcohol  and  water.  It  is  known  officially  as  Morphines 
Ac  etas. 

46 1 .  Morphine  hydrochlorate,  (Ci7Hi9NOs)HC1.3H20,also 
known  as  the  hydrochloride  or  muriate,  occurs  in  the 
form  of  snow-white,  feathery,  flexible,  acicular  crystals,  of 
bitter  taste  and  silky  lustre,  wholly  soluble  in  both  alco- 
hol and  water.  Morphinae  Hydrochloras  or  Murias  is  the 
official  term. 

462.  Morphine  sulphate,^  (CnHi9N03)2H2S04.5H20,  oc- 

*  To  test  the  hydrochlorate  (muriate)  of  cocaine,  take  1^^  grains 
cocaine  muriate  and  dissolve  in  80  minims  of  distilled  water;  add  2 
drops  of  dilute  C.  P.  sulphuric  acid,  then  1  drop  of  a  1  to  100  solution 
of  potassium  permanganate  in  distilled  water.  Instant  discolora- 
tion, or  in  less  than  one  minute,  shows  presence  of  organic  impurities. 
The  purest  is  said  not  to  discolor  in  an  hour.  Comparative  tests, 
that  is  of  several  samples  at  a  time,  are  desirable. 

t  For  hypodermic  \xs&,\}i\Q phtalate  oi  morphine  is  recommended. 
It  comes  in  transparent,  glassy  scales,  and  is  said  not  to  be  so  liable 
to  decomposition  as  the  sulphate. 


303  DENTAL   CHEMISTRY. 

curs  in  form  of  crystals  like  the  hydrochlorate,  neutral 
in  reaction,  odorless,  with  bitter  taste,  soluble  in  both 
water  and  alcohol. 

463.  In  dentistry  the  salts  of  morphine,  especially 
the  acetate  and  the  hydrochlorate,  are  used  in  devitalizing- 
mixtures  and  as  obtunding  agents,  also  for  temporary  re- 
lief of  odontalgia,  usually  in  combination  with  carbolic 
acid,  oil  of  cloves,  etc.,  etc.  The  acetate  is  used  in  nerve 
paste,  rather  than  the  sulphate,  which  latter  is  thought 
more  irritating.  Morphine  is  also  given  internally,  in 
facial  neuralgia,  etc.  The  average  fatal  dose  of  the  salts 
of  morphine  is  2  grains.  Treatment  of  poisoning  by  these 
agents  should  consist  in  the  use,  by  all  means,  of  the 
stomach  pump,  washing  out  the  stomach  either  with  an 
infusion  of  coffee  or  green  tea,  or  else  with  water  in  which 
finely  powdered  charcoal  is  suspended,  using  a  fresh 
amount  for  each  injection.  If  the  pump  is  not  used, 
vomiting  should  be  encouraged,  zinc  sulphate  in  5  grain 
doses,  with  fifteen  minute  intervals,  being  given,  or  apo- 
morphme hydrochlorate  s\xhc\xid,r\.QOus\y ,  in  doses  of  from  1-15 
to  1-5  of  a  grain.  Subsequently,  1 5  drops  of  tinctiire-of  bel- 
ladonna, or  1-35  grain  of  atropine  sulphate  (subcutaneous- 
ly  ),  should  be  given.  In  the  early  stages  of  poisoning  the 
above  mentioned  treatment  is  often  all  that  is  necessary. 
In  later  stages  artificial  respiration  and  use  of  the  battery 
(Faradic  current)  are  imperative.  Enemata  of  strong 
coffee  may  be  administered. 

464.  Qninine;  C2oH24Ni;02  +  3H2O.  This  alkaloid  oc- 
curs in  cinchona  bark,  together  with  a  number  of  others 
of  which  cinchona,  quinidine,  and  cinchonidine  are  the 
most  important.  Quinine  (crystallized), is  a  white  powder, 
of  bitter  taste  and  alkaline  reaction.  It  is  nearly  insolu- 
ble in  water.  Quinine  itself  is  seldom  used.  Salts  of  it 
are  sulphates,  hydrochloride,  salicylate,  tannate,  hydro- 
bromide,  valerianate,  citrate  (of  iron  and  quinine),  hypo- 


ORGANIC   CHEMISTRY.  309 

phosphite.     The  sulphate,  disulphate,  hydrobromide,  hy- 
drochloride, and  valerianate,  are  official. 

465.  Quinine  Sulphates:  there  are  three  of  these,  of 
which  the  diquinic  sulphate  (C;;oH24N20a)2H2SOi.7H20, 
is  the  official  sulphate.  It  occurs  as  long,  brilliant 
needles,  efflorescing  to  a  white  powder.  It  is  but  spar- 
ingly soluble  in  water:  i  in  780  parts;  in  alcohol,  i  in  65. 
It  is  readily  soluble  in  dilute  acids,  but  nearly  insoluble 
in  ether  or  chloroform. 

The  official  bisulpJiatc  is  obtained  by  dissolving  the  sul- 
phate in  dilute  sulphuric  acid.  Its  formula  is  CaoHaiNaOa. 
H,>SO,  .7HA 

There  is  another  sulphate,  obtained  by  dissolving  qui- 
nine in  excess  of  dilute  sulphuric  acid.  Its  formula  is 
(QoH2iN202)2H2SOi.7H,0.  It  is  not  official.  There  is  also 
a  hypophosphite. 

466.  The  salts  of  quinine  are  used  in  dentistry  in 
the  treatment  of  various  facial  and  neuralgic  affections 
and  as  ingredients  of  dentifrices. 

467.  The  alkaloi<ls  of  Nux  Vomica: — 

Strychnine,  Strychninum,  strychnia,  CaiHjoN^Oa.  Occurs 
in  seed  of  Strychnos  Nux  Vomica,  or  poison-nuttree; 
also  in  Strychnos  Ignatia,  or  St.  Ignatius  bean,  found  as 
strychnate  or  acetate. 

Brucine  is.  the  other  alkaloid,  and  is  more  soluble  than 
strychnine. 

The  bitter  taste  of  strychnine  is  perceptible  in  a  solu- 
tion containing  but  one  part  in  1,000,000.  Strychnine 
sulphate  (C2iH22NoO.,)2.H2SOi.7H20,  is  official,  and  readily 
soluble  in  water.  Salts  of  strychnine  are  very  poisonous, 
%  oi  7i  grain  having  caused  death.  The  treatment,  in 
cases  of  poisoning,  should  consist  in  inhalation  of  chloro- 
form, use  of  emetics,  and,  if  possible,  the  injection  into 
the  stomach  and  withdrawal  therefrom  of  powdered  char- 
coal.    Chloral  hydrate   and  paraldehyde  are    sometimes 


310  DENTAL    CHEMISTRY. 

administered  as  antidotes,  and  chloroform  given  intern- 
ally. 

468.  Yeratriiie:  CstHmNOh,  is  an  alkaloid  found  in 
Vcratnun  sabadilla  and  in  Ccvadilla,  the  seeds  of  Asagrcca 
officinalis:  also  in  Vcratrum  album  ox  white  hellebore,  and 
Veratrum  viridc,  or  American  hellebore.  It  occurs  as  a 
white,  or  grayish-white  amorphous  powder,  of  acrid  taste; 
it  causes  violent  sneezing,  if  inhaled.  The  olcate  of  vera- 
trine  is  official,  and  is  made  to  contain  2  per  cent,  of  the 
alkaloid,  and  also  ten  per  cent. 

In  dental  practice,  veratrine  in  form  of  ointment  is  used 
for  neuralgia,  etc. 

469,  Other  alkaloids: — 

Antipyrine,  dimethyloxyquinizine,  useful  as  an  adjunct 
to  cocaine  in  dental  ansesthetization.  Synthetic  alkaloid. 
Formula,  CnHioNoO.  White,  crystalline,  odorless,  bitter 
tasting  powder. 

Antifcbrin  or  acetanilide. 
(  CeHj       crystalline,  odorless,  solid; 
N  ■(  H  slightly  soluble  in  warm  water; 

/  CoHijO:  very  soluble  in  alcohol. 
Synthetic  alkaloid. 

Ahtoninc,  the  alkaloid  of  Alstonia  cojtstricta.  White 
crystals. 

Apoviorpldnc,  emetic. 

Caffeine :  a  new  compound  is  the  boro-citratc  of  caffeine. 

Cytisine,  alkaloid  of  Cytisiis  labnmmn. 

Ditaine,  C22H30N0O4,  alkaloid  of  Dita-bark  from  Alstoni- 
ca  scholaris. 

Erythrophlcim  from  Erythrophleum  bark;  said  to  be  a 
local  anaesthetic, 

Ethyl-oxy-Caffeine,  C8H9(O.C2H5)N402,  used  as  a  local 
anaesthetic  by  subcutaneous  injection. 

Hyoscyamine  from  the  black  Hyoscyamus  plant;  cser- 
ine  from  calabar  bean;  narceine  from  opium. 


ORGANIC   CHEMISTRY.  312 

h-atropyl  Cocaine,  CigHajNOi,  obtained  as  secondary  pro- 
duct in  manufacture  of  cocaine  and  thought  to  be  possi- 
bly the  cause  of  toxical  accessory  symptoms  consequent 
on  the  administration  of  even  slightly  impure  cocaine. 

ycriibebint\  alkaloid  of  Solamim  paniculaUim. 

Laminc  from  flowers  oi  Lamium  album;  hemostatic. 

Oxy-propylenc-di-iso-amyl-amine:  synthetic,  alkaloid. 
Colorless  liquid. 

Ulcxine,  alkaloid  from  Genista  tinctoria. 

Newer  Alkaloids,  Glucosides  etc. 

Arbutin,  glucoside  of  uva  ursi.    Diuretic. 

Arecoline,  alkaloid  from  areca  nut;  alkaline  liquid. 

Aspiclospermine,  mixture  of  Quebracho  alkaloids. 

Bebeerine-alkaloid  from  nectandra  rodiaei — not  ber- 
berine. 

Boldine,  alkaloid  of  Boldo  Chiliensis. 

Convallarin,  c/lucoside  from  convallaria,  insoluble  in 
water,  drastic  purgative. 

Convallamarin,  glucoside  from  convallaria  majalis, 
soluble  in  water,  powerful  heart  tonic. 

Diuretin,  is  theobromine  sodium  salicylate. 

Mtiawin,  glucoside  from  the  muawi  tree.  Resembles 
digitalin. 

Narceine  {hydrochlorate),  hypnotic  alkaloid  from  opium. 

Papaverine  (Jii/drochlorate)  alkaloid  from  opium. 

Piperine,  alkaloid  from  piper  nigrum. 

Tropa-cocaine  the  alkaloid  from  Javanese  coca. 

Nicotin,  CoHj^N,,  from  tobacco.  Liquid.  Sp.  gr.  1027. 
Soluble  in  water. 

Coniln,  QHiyN,  liquid,  from  comum  maculatum.  Has 
been  prepared  artificially. 

Sparteine,  CuFL-ftN,,  liquid. 

The  three  above  are  known  as  volatile  alkaloids,  color- 
less when  pure  and  first  separated,  but  turning  brown  on 


312  DENTAL    CHEMISTRY. 

exposure  to  the  air.    They  have  disagreeable,  penetrating 
odor.     The  following  are  also  alkaloids: 

Lohelin,  Indian  tobacco,  liquid. 

Sophorin,  Sophora  Japonica,  liquid. 

Apomorphine,  CnHi^NOa,  made  by  heating  morphine 
with  HCl  to  about  300  F. 

Honiatropin  from  atropine. 

Colchicine  C17H19NO5  from  colchicum  autumnale. 

Theine  is  of  the  same  formula,  source,  and  properties. 
'  Theobromine  CxiVi^^iO 2,  is   from   cacao.      Crystals,  not 
very  soluble  in  water. 

Piperine,  CnHjgNOa,  cayenne  pepper,  yellow  crystals, 
isomeric  with  morphine. 

Pilocarpine,  CnHigNaOj,  from  jaborandi;  increases  per- 
spiration. 

Pelletierin,  CgHjgNO,  is  from  the  pomegranate  root  and 
is  a  liquid. 

Adonidin,  glucoside  from  adonis  vernalis;  cardiac  tonic. 

Arecoline,  alkaloid  from  areca  nut.  Powerful  anthel- 
mintic and  heart  poison. 

Baptisin,  g\\xcos\dQ  from  baptisia  tinctoria.  Purgative, etc. 

Caffeine,  CgHjoNiOo,  is  the  alkaloid  of  coffee;  it  is  solu- 
ble in  water  and  of  feeble  basic  properties.  New  salts, 
very  soluble,  are  the  sodio-benzoate,  sodio-cinnamate, 
sodio-citrate,  sodio-salicylate,  sodio-borocitrate,  phenate, 
and  phthalate. 

Coronillin,  glucoside  from  coronilla  scorpoides. 

Digitalin,  digitalein,  a.nd  digitoxin ,  alkaloids  of  digitalis 
the  last  the  most  poisonous. 

Euryhin,  glucoside  from  eurybia  moschata. 

Euonymin,  resin  from  eunonymus  atropurpureus. 

Lactucin,  active  principle  of  lactucarium.     Hypnotic. 

Lantanine,  alkaloid  from  lantana  brasiliensis. 

Leptandrin,  glucoside  from  leptandra. 


ORGANIC    CHEMISTRY.  313 

Ouabain,  glucoside  from  wood  of  acocanthera  ouabaio. 
Papain,  digestive  ferment  from  carica  papaya. 
Scoparine,  active  principle  of  cytisus  scoparius.  Diu- 
retic. 
Scopolamine,  alkaloid  of  scopolia  atropoides.  Mydriatic. 
Spasmotin,  sphacelotoxin,  poisonous  principle  of  ergot. 
Strophanthine  glucoside  from  strophanthus.  Heart  tonic. 
Solanine,  alkaloidal  glucoside  from  the  solanaceae. 

ALBUMINOUS     SUBSTANCES. 

470.  Proteids:  a  certain  amount  of  knowl- 
edge in  reg^ard  to  these  substances  is  essential. 
Proteid  is  the  general  term  given  to  albumi- 
nous compounds,  which  form  the  chief  part  of 
the  solids  of  the  organs,  blood,  muscle  and 
lymph  of  animals,  and  seeds  of  plants.  They 
are  not  crystalline,  but  colloid,  do  notid  ffuse 
through  animal  membranes,  and  readily  pu- 
trefy when  exposed  to  the  air.  They  are  white, 
flaky  or  granular,  amorphous,  and  difficult  to 
obtain  in  the  pure  state. 

Some  are  soluble,  others  insoluble  in  water;  they  are 
soluble  in  mineral  acids  and  caustic  alkalies,  but  almost 
insoluble  in  alcohol  and  ether.  They  have  the  peculiar 
property,  however,  of  becoming  insoluble  either  sponta- 
neously, or  after  action  of  heat,  or  under  influence  of 
weak  acids.  They  all  yield  what  seems  to  be  the  same 
substance,  syntonic,  and,  under  the  influence  of  the  gastric 
juice,  they  are  capable  of  generating  peptones,  or  bodies 
easily  assimilated  and  very  nutritious.  Proteids,  when 
heated,  do  not  volatilize,  but,  when  burnt,  they  give  off 
products  having  odor  of  burnt  horn. 


314  DENTAL   CHEMISTRY. 

No  accurate  formulae  have  been  fourjrd  foi 
proteids,  but  they  are  known  to  contain  car- 
bon, hydrogen,  nitrogen,  oxyg^en,  sometimes 
sulphur,  sometimes  phosphorus,  and  iron  ;  in 
their  ash,  calcium  phosphate  is  found.  Their 
percentage  composition,  according-  to  Wurtz, 
is  carbon  52.7  to  54.5,  hydrogen  6.9  to  7.3,  ni- 
trogen 15.4  to  17,  oxygen  20.9  to  23.5,  sulphur 
0.8  to  2.2. 

471.  Proteids  heated  with  a  solution  of  mercurous  ni- 
trate, containing  nitrous  acid,  assume  a  fine  red  color. 
On  exposure  to  the  air,  proteids  putrefy  readily,  fine 
granulations  being  developed  in  their  interior,  which 
change  into  vibrios,  oxygen  at  the  same  time  being  ab- 
sorbed, while  carbon  dioxide  (carbonic  acid  gas),  nitro- 
gen, ammonia,  sulphuretted  hydrogen,  hydrogen,  am- 
monium sulphide,  are  discharged,  and  fatty  acids,  as 
butyric,  lactic  acid, — amines,  leucin,  tyrosin,  etc.,  formed. 

472.  Proteids  are  classified  by  Hoppe-Seyler  as  fol- 
lows : 

1.  Native  albumins:  soluble  in  water  and  precipitated 
by  boiling;  albumin  of  serum  (blood  albumin)  and  albu- 
min of  white  of  &z^^.  Blood  albumin  is  coagulated  by  a 
temperature  of  from  I22"F.  to  163°,  but  not  by  ether. 
Egg  albumin  begins  to  coagulate  at  129",  coagulation  in- 
creasing at  145°  and  165°;  it  is  precipitated  by  ether. 
Blood  albumin,  in  solution,  may  be  precipitated  by  con- 
centrated nitric  acid,  citric  or  acetic  acid  plus  potassium 
ferrocyanide,  picric  acid,  and  by  many  other  substances. 

2.  Globulins:  insoluble  in  water,  soluble  in  i  per  cent, 
sodium  chloride  solution,  but  precipitated  (except  vitel- 
lin)  by  saturated  solution  of  common  salt  or  by  addition 
of  large  quantity  of  water.     The  globulins   are    vitellin. 


ORGANIC   CHEMISTRY.  315 

crystallin,  fibrinogen,  fibrino-plastin,  myosin  or  muscle 
fibrin.  Syntonin  may  be  prepared  from  myosin  by 
treating  the  latter  with  a  very  little  HCl. 

Fibrin:  a  v.hite,  elastic,  more  or  less  fibrillated  solid, 
insoluble  in  water  and  dilute  sodium  chloride  solutions, 
prepared  by  rapidly  stirring  freshly  drawn  blood  with  a 
bundle  of  twigs,  and  washing  the  coagulum  with  water. 
Neutral  solutions  of  fibrinogen  and  fibrinoplastin,  mixed, 
in  presence  of  fibrin  ferment  form  fibrin.  Fibrin  does 
not  dissolve  in  i  per  cent,  solution  of  HCl,  but  swells, 
becoming  soluble  on  addition  of  pepsin.  Fibrin  coagu- 
lates spontaneously  on  exposure  to  air. 

4.  Albuminates  or  derived  albumins,  sometimes  called 
modified  albumins:  these  are  (i)  acid  albuminate,  known 
also  as,  syntonin,  albumose,  and  parapeptone,  and  (2) 
alkali-albuminate  found  in  blood  corpuscles,  blood  serum, 
etc.,  and  closely  resembling  casein. 

5.  Peptones:  albuminous  bodies  are  converted  by  the 
action  of  the  gastric,  pancreatic,  and,  doubtless,  intestinal 
juices,  into  more  diffusible  and  soluble  bodies  called  pep- 
tones. 

6.  Amyloid  substance  or  lardacein. 

7.  Coagulated  albumin,  as  produced  by  action  of  heat 
on  solution  of  serum  albumin. 

8.  Special  albumins  found  in  cysts,  dropsical  fluids, 
etc.     (Metalbumin,  paralbumin). 

9.  Collagens:  albuminous  bodies  which  do  not  yield 
syntonin  wdien  treated  with  dilute  acids.  Hot  aqueous 
solutions  become  jelly-like  on  cooling.  The  collagens 
are  ossein,  gelatin,  chondrin,  mucin,  and  elastin.  Ossein 
is  the  proteid  basis  of  bones,  and  contains  49.9  per  cent, 
of  carbon,  7.3  of  hydrogen,  17.2  of  nitrogen,  24.9  of  oxy- 
gen, and  0.7  of  sulphur.  Chondrin  is  the  proteid  found  in 
cartilages. 

473.     IShiciii  is  found  in  several  parts  of  the  body  and  is 


316  DENTAL  CHEMISTRY. 

one  of  the  excretion  products  of  the  protoplasm  of 
epithelial  cells  lining  mucous  surfaces,  and  of  the  secreting 
mucous  cells  of  the  sublingual  and  submaxillary  glands. 
Its  average  composition  is  49.5^  carbon,  6.7^  hydr,ogen 
9.6^  nitrogen,  and  34.2^  oxygen.  Dry  mucin  yields 
about  2.44^  ash  and  contains  no  sulphur.  In  chemical 
constitution  it  is  a  nitrogenous  glucoside  and  probably  an 
albumin  derivative.  Mucin,  when  obtained  in  the  free 
state,  occurs  in  white  or  yellow,  thready,  tenacious 
masses.  It  swells  in  water  and  mixes  with  it,  but  does 
not  dissolve.  It  is  soluble  in  dilute  HCl,  in  weak  alkalies, 
but  insoluble  in  alcohol,  ether,  chloroform,  dilute  acetic 
acid,  very  dilute  mineral  acids.  Acetic  acid  makes  it 
shrink  ;  caustic  potash  makes  it  more  thready  at  first, 
then  dissolves  it.  Its  solutions  are  precipitated  by  acetic 
acid,  and,  according  to  Oliver,  by  alcohol,  dilute  mineral 
acids,  and  all  vegetable  acids. 

Elasticin  or  (elastin)  is  the  proteid  composing  the 
fibres  cf  yellow  elastic  tissue. 

474.  10.  Proteid  derivatives:  leucin,  C6H13NO2,  or  ami- 
docaproic  acid,  is  an  important  proteid  derivative,  and  is 
a  constant  product  of  the  decomposition  of  albumin  and 
of  nitrogenous  substances.  It  is  formed  in  decomposing 
cheese.  Tyrosin,  CgHnNOj,  is  also  a  proteid  derivative. 
Both  are  occasionally  found  in  the  saliva.  Both  unite 
with  both  acids  and  bases. 

475.  II.  Nitrogenized  products  of  tissue  metabolism: 
uric  acid,  sarkin,  xanthin,  guanin,  etc.,  etc.  Uric  acid, 
C5H4N4O3,  is  found  in  calculi,  blood,  urine,  etc.,  etc.  It  is 
very  sparingly  soluble  in  water.  It  forms  urates,  of  which 
lithium  urate  is  the  most  soluble.  Compounds  of  lith- 
ium are,  therefore,  administered  in  cases  of  uric  acid 
calculi. 

476.  Fermentation:  according;  to  Gautier, 
fermentation  takes  place  whenever  an  organic 


ORGANIC   CHEMISTRY.  317 

compound  undergoes  changes  of  composition 
under  the  influence  of  a  nitrogenous,  organic 
substance,  called  a  ferment,  which  acts  in 
small  quantities  and  yields  nothing  to  the  fer- 
mented substance.  In  a  word,  fernientatioji 
is  the  decomposition  of  carbo-hydrates  into 
simpler  compoimds,  by  the  agency  of  living 
microbes. 

Putrefaction  is  the  name  given  to  decom- 
position-fermentations in  animal  or  vegetable 
organisms  rich  in  proteids;  in  putrefaction, 
offensive  odors  are  given  off.  Neither  fer- 
mentation nor  putrefaction  is  simply  oxida- 
tion, but  the  presence  of  oxygen  appears  to  be 
necessary  to  set  up  the  change.  The  presence 
of  water  is  also  necessary  to  processes  of  fer- 
mentation. 

477.  Ferments:  ferments  are  in  general  of 
two  kinds  (i)  soluble  or  unorganized  (en- 
zymes, and  (2)  organized. 

478.  Soluble  or  unorganized  ferments  are  proteid 
substances  having  the  power,  under  favorable  circum- 
stances, of  causing  certain  chemical  changes  in  bodies 
with  which  they  come  into  contact,  whilst  they  themselves 
undergo  no  change.  Several  soluble  ferments  are  of 
vegetable  origin,  and  of  these  diastase  is  the  most  import- 
ant; those  of  animal  origin  are  pepsin,  ptyalin,  trypsin, 
etc.,  etc.  They  are  soluble  in  water,  very  diffusible,  and, 
although  not  precipitated  by  boiling,  nevertheless  lose 
their  activity.  They  neither  give  to  the  bodies  with 
which    they    are    brought    in    contact    nor   take   from 


318  DENTAL   CHEMISTRY. 

them.  Their  activity  is  destroyed  by  borax,  but  not  by 
hydrogen  dioxide.  They  do  not  reproduce  themselves 
during  the  period  of  their  activity. 

479.  Diastase  (maltin)  is  the  ferment  formed  in  grains, 
at  time  of  sprouting,  from  the  gluten.  It  converts  starch 
into  dextrin  and  maltose.  Ptyalin,  the  salivary  ferment, 
has  the  same  action;  they  act  slowly  on  unchanged 
starch,  but  rapidly  on  cooked  starch.  The  starch  is  first 
liquefied,  then  converted  into  dextrin,  then  into  maltose. 
The  amount  of  starch  that  can  be  transformed  is  any- 
where from  2,090  to  100,000  times  the  weight  of  the  fer- 
ment. 

480.  Pepsin  is  secreted  in  the  glands  of  the  stomach. 
It  is  obtained  from  the  stomach  of  the  pig  by  digesting 
the  mucous  membrane  in  hydrochloric  acid,  and  precipi- 
tating by  sodium  chloride.  It  is  a  yellowish  or  grayish- 
white  powder,  insoluble  in  water,  but  soluble  in  water  to 
which  glycerine  has  been  added.  It  is  of  peculiar  odor, 
and  bitter,  nauseating  taste.  Heat  of  230"F.  decomposes 
it  and  renders  it  inert,  but  its  solutions  lose  activity  at 
much  lower  temperatures.  The  temperature  most  favor- 
able for  its  activity  is  98.6'*F.,  and  presence  of  a  dilute 
acid  as  hydrochloric,  lactic,  phosphoric,  etc.,  is  required 
to  develop  its  peculiar  action,  /oth  per  cent.  NaCl  also 
favors  its  action,  but  half  of  one  per  cent,  hinders  it. 
Carbolic  acid  or  excess  of  alcohol  retards  its  action.  In 
dental  practice,  pepsin  is  used  in  the  treatment  of  putrid 
pulps,  as  an  antiseptic  and  deodorizer. 

It  has  been  used  and  recommended  by  Coleman,  of 
England,  to  digest  dead  pulp  in  inaccessible  teeth,  dilute 
hydrochloric  acid  being  employed  along  with  it. 

481.  Organized  ferments:  soluble  ferments,  as  we 
have  seen,  are  responsible  for  all  physiological  fermenta- 
tions; on  the  other  hand,  pathological  fermentations  are 
caused  by  organized  ferments,  which  are  forms  of  low  or- 


ORGANIC   CHEMISTRY. 


319 


ganisms,  vegetable  in  origin,  whose  activity  is  greatest 
at  temperatures  ranging  from  68°F.  to  about  104°,  Their 
activity  is  retarded  by  temperature  below  or  above  these 
limits,  and  temperatures  near  2I2°F.  entirely  destroy 
their  activity,  as  does  also  hydrogen  dioxide.  The  latter 
agent  stops  also  the  chemical  changfe  which  is  the  direct 
result  of  the  growth  of  the  organized  ferments.  These 
ferments  are  remarkable  in  that  a  very  minute  quantity 
will  grow  and  exert  its  action  as  long  as  appropriate 
nourishment  is  furnished  it.  Organized  ferments  have, 
then,  powers  of  growth  and  reproduction,  and  the  ferment 
power  cannot  be  separated  from  the  ferment  organism  by 
filtration  or  by  any  solvent.  The  chief  food  of  organized 
ferments  is  ammoniacal  salts  and  alkaline  phosphates. 
The  most  important  of  the  organized  ferments  are  yeast 
(alcoholic  ferment)  acetic  acid  ferment,  lactic  and 
butyric  acid  ferment,  the  ferment  of  "thrush,"  and  the 
putrefactive  ferments. 

482.  Yeast  spores  are  always  to  be  found  either  in  the 
air,  or  on  fruit.  Their  chief  action  is  to  convert  sac- 
charose into  grape  sugar,  and  then  to  change  the  latter 
into  alcohol  and  carbonic  acid  with  a  trace  of  succinic 
acid  and  glycerine.  The  equation  of  the  change  due  to 
yeast  would  be  : 

QH12O0      +      2HvO     =     2QH6O     +     2H2CO3 

Glucose.  Water.  Alcohol.  Carbolic  acid. 

Yeast  is  known  as  Tonila  {Saccharoinyces)  cere  visits. 

483.  The  acetic  acid  fermetit  belongs  to  the  bacteria 
family  and  grows  in  alcoholic  solutions  containing  a  little 
albuminous  matter  or  various  salts,  as  those  of  ammon- 
ium, or  alkaline  and  earthy  phosphates.  It  acts  by  oxi- 
dation changing  alcohol  to  acetic  acid,  the  mycodertna 
aceti  acting  as  an  oxygen  carrier. 

484.  ThQ  lactic  acid fer7)ie)it  grows  in  a  neutral  or  alka- 
line medium  and  best  without  oxygen,  at  a  temperature 


320  DENTAL   CHEMISTRY. 

of  from  QS^F.  to  I04°F.  Various  kinds  of  sugar  and  dex- 
trine, under  the  action  of  bacterium  lactis,  are  converted 
into  lactic  acid  in  the  presence  of  a  decomposing  albu- 
minous substance,  especially  casein,  and  water.  The  pro- 
cess is  also  favored  by  presence  of  chalk,  or  alkaline  car- 
bonates, which  neutralize  the  lactic  acid  as  fast  as  it  is 
formed;  were  it  not  for  this  neutralization,  the  production 
of  acid  would  prevent  the  continuance  of  the  fermenta- 
tion.    The  equation  is  as  follows: 

Ci^H^^On       -j-       H,0      =       2CeH,eOe       +    4QHeO. 
Lactose.  Water.  G.ucose.  Lactic  acid. 

also 

CaH^aOe  -  2C3H«03 

Glucose.  Lactic  acid. 

Lactic  acid  is,  according  to  Miller,  formed  in  the  teeth 
during  caries. 

485.  The  butyric  ferment  goes  hand  in  hand  with  the 
lactic.  Lactic  acid  is  split  up  by  its  agency  into  butyric 
acid,  carbon  dioxide,  and  hydrogen. 

2C3H6O:,     =      C.H^Oa     -f     2C02     +     2H 

Lactic  acid.  Butyric  acid.       Carbon.  Hydrogen. 

dioxide. 

486.  l^\\e  thrush  ferment  IS  3.  fungus,  which  appears  on 
the  mucous  membrane  of  the  mouths  of  infants,  es- 
pecially of  those  brought  up  by  hand.  The  saliva  be- 
comes acid  and  white  spots  appear,  especially  on  the 
tongue,  gums,  and  soft  palate. 

487.  Various  forms  of  bacteria  cause  putre- 
factive fernieritation  in  proteids,  by  which  the 

latter  are  decomposed  into  fats,  tyrosin,  leu- 
cin,  ammonia,  sulphuretted  hydrogen,  carbon 
dioxide,  hydrogen,  and  nitrogen.  //  is  from 
the  decomposition  of  proteids  that  the  sidphur- 
etted  hydrogen  in  the  nionth  is  formed. 

488.  Classification  of  Bacteria,  etc.:  the  term  microbe 
is  used,  in  general,  to   designate   the  minute  organized 


ORGANIC   CHEMISTRY.  321 

beings  which  are  found  on  the  borderland  between  ani- 
mals and  plants;  in  the  majority  of  cases  they  may  be 
regarded  as  true  plants.  Broadly,  microbes  may  be  divi- 
ded'into /^rrt^zVzV ///;z^2  and  moulds,  ferments,  and  bacteria, 
and  to  the  last  the  term  microbe  in  particular  is  usually 
applied. 

489.  Fungi  are  plants  devoid  of  stems,  leaves,  and 
roots;  they  consist  only  of  cells  in  juxtaposition,  devoid 
of  chlorophyll;  they  never  bear  a  true  flower  and  are 
simply  reproduced  by  means  of  very  minute  bodies,  usually 
formed  of  a  single  cell,  called  a  spore  and  representing  the 
seed.  Among  the  parasitic  fungi  and  moulds  may  be 
found  the  rust  of  wheat  and  grasses,  the  ergot  of  rye, 
mould  of  leather  and  dried  fruit,  potato  fungus,  mildew, 
the  fungi  of  certain  skin  diseases  as  tinea,  thrush,  etc. 

490.  Ferments  are  closely  allied  to  a  variety  of  fungus 
called  microsporon,  but  as  they  live  in  liquids  or  on  damp 
substances  they  are  classified  by  many  among  the  Algae, 
a  species  of  water  fungi.  Ferments,  however,  differ  from 
Algns  in  not  containing  chlorophyll.  Each  plant  of  the 
ferment  variety  is  usually  composed  of  a  single  cell, 
spherical,  elliptical,  or  cylindrical,  formed  of  a  thin  cell- 
wall,  containing  a  granular  substance  called  protoplasm*, 
which  is  the  essential  part  of  the  plant.  The  cells  have 
an  average  diameter  of  ten  micro-millimetres;  they  grow 
and  .bud,  and  each  divides  into  two  parts.  Among  the 
ferments,  we  find  those  of  wine,  beer-yeast,  bread-yeast, 
etc.,  etc. 

491.  Bacteria  are  alike  in  form  and  organization  to 
ferments,  but,  as  a  rule,  are  of  smaller  size.  Microbes  or 
bacteria  (Schizophyta   or  Schizomycetes)  appear,  under 

*  The  composition  of  protoplasm  is  essentially  proteids,  water,  cer- 
tain mineral  matters,  fats,  starch,  and  sugar. 


322  DENTAL   CHEMISTRY. 

the  microscope,  as  small  cells  of  a  spherical,  oval,  or  cyl- 
indrical shape,  sometimes  detached,  sometimes  united  in 
pairs,  or  irt  articulated  chains  and  chaplets.  The  diame- 
ter of  the  largest  of  these  cells  is  but  two  micro-millirne- 
tres,  and  that  of  the  smallest  is  a  fourth  of  that  size.  A 
power  of  from  500  to  1,000  diameters  is  necessary  to 
make  them  clearly  visible  under  the  microscope. 

Morphologically,  Dujardin-Beaumetz  recognizes  six 
forms:  ( i )  Monad,  micrococcus,  or  moner,  immobile  point- 
like microbes,  often  regarded  as  spores.  (2)  Bacteridia 
and  bacillus,  immobile,  linear  microbes.  (3)  Bacteriens, 
cylindrical  mobile  microbes,  the  end  rounded,  or  the 
body  indented  in  the  centre,  so  as  to  form  a  figure  of  8. 
(4)  Vibriones,  eel-shaped,  undulating,  mobile  and  flexuous 
microbes,  (5)  Spirilla  and  spirochcete,  corkscrew-like, 
spirally  moving  microbes.  (6)  Capitated  microbes.  Bac- 
terium capitatuni,  mobile  rods,  with  one  or  both  extremi- 
ties long,  globular,  and  more  refractive  than  the  rest  of 
the  body. 

This  classification  has  reference  to  the  cells  as  seen 
singly  or  in  very  limited  numbers;  when  aggregated  so  as 
to  form  colonies  there  are  distinguished  four  forms: 

1.  Torula,  in  the  form  of  a  necklace,  composed  of 
micrococci. 

2.  Leptothrix,  made  up  of  bacteria,  clustered  end  to 
end. 

3.  Mycoderma,  immobile,  composed  of  bacteria  in 
sheets. 

4.  ZooglcEa,  being  masses  of  bacteria,  immobile,  in- 
closed in  a  sort  of  jelly  which  holds  them  together. 

492.  Varied  conditions  of  existence  influence  the  form 
taken  by  these  organisms,  so  that  distinctions  into  genera 
and  species  are  not  as  yet  made  on  precise  data.  The 
microbe  of  acetic  fermentation  is  a  true  bacterium  ( bacter- 


ORGANIC    CHEMISTRY.  323 

ien).     The  microbe  of  lactic  fermentation  \?,  also  a  bacter- 
ium.    The  microbe  of  butyric  fermejitation  is  a  bacillus. 

493.  In  putrefaction,  or  fermentation  of  dead  organic 
matter  exposed  to  the  air,  the  substances  are  first  rapidly 
cov^ered  with  moulds,  they  lose  coherence,  and  after  a  few 
days  give  off  carbonic  acid,  nitrogen,  hydrogen,  and  fetid 
effluvia,  due  largely  to  carburetted,  'sulphuretted,  and 
phosphoretted  hydrogen,  and  to  the  circulation  of  de- 
composing organic  particles.  The  microbes  which  appear 
simultaneously  with  the  moulds,  penetrate  deeply  into  the 
tissues,  disintegrate  them  by  feeding  at  their  expense, 
and  the  putrid  condition  increases;  then  the  decomposi- 
tion changes  its  nature  and  becomes  less  intense.  The 
putrefied  matter  is  finally  dessicated,  and  leaves  a  brown 
mass — a  complex  mixture  of  substances  combined  with 
water  and  of  fatty  mineral  substances,  wdiich  gradually 
disappear  by  slow  oxidation.  (Gautier).  In  such  putre- 
faction of  animal  matter  in  water  are  found  microbes  in 
the  form  of  globules  or  short  rods  {^Micrococcus,  Bacterium 
tcrmo.  Bacillus,  ^/t.),  either  free,  or  in  a  semi-mucilaginous 
mass  to  which  the  term  Zooglcea  has  been  given.  These 
microbes  deprive  the  liquid  of  all  its  oxygen.  A  thin 
layer  on  the  surface  absorbs  oxygen;  in  the  interior,  al- 
buminoid matter  is  changed  into  more  simple  substances, 
and  the  microbes  on  the  surface  change  the  latter  into 
gases.  A  substance  remains  rich  in  fats,  earthy  and  am- 
monical  salts,  and  fit  to  serve  as  nutriment  to  plants. 

494.  The  microbes  of  the  mouth  of  a  healthy  man 
are  numerous,  and  include  (i)  Spirochoete,  (2)  a  species 
of  Sarcina,  and  (3)  more  especially,  a  large  organism 
called  Lcptothrix  buccalis  which  is  never  absent  from  the 
rough  surface  of  the  tongue  nor  the  interstices  of  the 
teeth.  The  saliva  contains  a  micrococcus  which  may  be- 
come exceptionally  virulent. 

The  microbe  of  dental  caries:  according;  to 


324  DENTAL   CHEMISTRY. 

Miller,  dental  caries  is  chiefly  due  to  the  de- 
velopment of  one  or  more  species  of  bacteria. 
The  microbe  most  common  in  decayed  teeth 
is  very  polymorphic,  micrococciLS,  bacterium, 
chains,  and  filaments  are  found,  all  different 
phases  of  the  same  plant,  which  is  responsible 
both  for  acid  fermentation  in  the  m.outh  and 
for  the  formation  of  lactic  acid. 

495.  The  microbe  of  pus,  as  found  in  blood  poisoning, 
is  termed  Micrococcus  septicus:  it  may  either  appear 
free  or  in  the  form  of  chaplets  {vibrio'),  or  in  the  interior 
of  the  colorless  corpuscles  of  pus,  or  embryonic  cells, 
which,  in  form  of  zooglcea,  it  ruptures.  The  germs  of  Mi- 
crococcus septicus  are  introduced  into  the  blood,  and 
multiply  there  through  the  exposed  surface  from  a  wound 
or  by  agency  sometimes  of  the  instrument  causing  the 
wound.  When  bacteria  multiply  in  the  blood,  they  must 
necessarily  have  an  irritating  effect  on  the  walls  of  the 
capillaries  and  the  cells  are  transformed  in  consequence 
into  embryonic  or  migratory  cells  which  differ  but  slightly 
from  the  colorless  blood-corpuscles  and  are  pus-corpus- 
cles.    (Trouessart). 

496.  Action  of  pathogenic  microbes:  this  is  complex 
and  is  analyzed  according  to  Trouessart  as  follows:  (i) 
the  action  of  a  living  parasite  nourished  by  and  multiply- 
ing at  the  expense  of  the  fluids  and  gases  of  the  system; 
(2)  the  formation  by  this  parasite  of  a  poisonous  sub- 
stance (ptomaine)  the  elements  of  which  are  derived 
from  the  organism,  and  it,  the  ptomaine,  acts  as  a  poison 
on  this  organism. 

497.  Pus  and  suppuration :  acccording  to  Knapp,  sup- 
puration in  every  case  depends  on  the  action  of  microbes. 
Pus  being  defined  as  an  albuminous,  non-coagulable  fluid 


ORGANIC   CHEMISTRY.  325 

containinc^  multitudes  of  leucocytes,  suppuration  is 
deemed  to  be  the  splitting  up  of  living  nitrogenous  tissue 
into  simpler  compounds  through  influence  of  certain  bac- 
teria. 

498.  Protection  against  microbes:  this  is 
to  be  accomplished  by  what  is,  in  general, 
called  disinfection.  Substances  used  for  the 
purpose  of  preventing  zymotic  diseases,  so- 
called,  have  been  classified  as  follows  : 

1.  Diluents:  air  and  water. 

2.  Absorbents:  dry  earth  and  plaster  of 
Paris. 

3.  Destructive  agents:  lime  and  sulphate  of 
iron  are  most  important.  Under  certain  cir- 
cumstances, permanganate  of  potassium,  caus- 
tic potash,  mineral  acids. 

4.  Antiseptics :  these  check  the  development 
of  the  organism  of  putrefaction  but  do  not 
necessarily  kill  disease  germs.  Most  import- 
ant: alcohol,  sulphate  of  iron,  borax.  Com- 
monly used:  salt,  saltpetre,  carbolic  acid. 

5.  Germicides :  agents  which  have  the 
power  of  killing  disease  germs;  most  import- 
ant are  chlorine  and  substances  which  con- 
tain it,  as  corrosive  sublimate.  All  germicides 
are  antiseptics,  but  the  antiseptics  proper  are 
not  germicides.  Nearly  all  bacteria  are  de- 
stroyed in  a  very  short  time  by  high  tempera- 
tures. 

499.  Antiseptics  are  used  in  dentistry  for 


326  DENTAL    CHEMISTRY. 

moistening  the  pellet  of  cotton  introduced 
into  a  cavity  which  is  to  be  sealed:  Harlan 
recommends  carbolic  acid,  aseptol,  creasote, 
terebene,  resorcin,  iodol,  iodoform,  beta-naph- 
thol,  eugenol,  pheno-resorcin,  eucalyptol,  thy- 
mol, myrtol,  menthol,  boroglyceride,  etc.,  etc., 
as  antiseptics. 

Disinfectants,  or  agents  which  will  destroy 
foul  odors  by  combining  with  them  chemically, 
and  will  cleanse,  purify,  and  destroy  infection 
are  used  in  the  treatment  of  engorged  antra, 
in  and  around  the  roots  of  teeth,  in  carious  or 
necrosed  bone,  on  buccal,  pharyngeal,  and 
laryngeal  mucous  membranes;  in  a  word, 
wherever  foul  odors,  infectious  material,  or 
decomposing  matters  are  found.  Harlan  rec- 
ommends Labarraque's  solution,  Condy's  fluid, 
aqueous  solution  of  zinc  chloride,  hydro- 
gen dioxide,  solutions  of  the  acetate  or  chlo- 
ride of  aluminium,  mercuric  chloride,  mer- 
curic iodide,  the  hypochlorites,  iodine,  resor- 
cin, trichlor-phenol,  boracic  acid,  benzoic 
acid,  etc. 

Smith  recommends  corrosive  sublimate  dis- 
solved in  hydrogen  dioxide.  Abbott  recom- 
mends half  a  grain  of  corrosive  sublimate  in 
twenty-one  fluidounces  of  water. 

Iodoform  and  eucalyptus,  iodoform  and  oil  of  cinna- 
mon, solutions  of  aluminium  chloride,  carbolic  acid  (with 
equal  parts  caustic  potash — Robinson's  remedy)  salicy- 


ORGANIC   CHEMISTRY.  327 

lie  acid,  carvacrol,  thymol  (in  glycerine)  chinoline  tar- 
trate, creasote,  eugenol,  resorcin,  Sanitas  oil,  Listerine, 
boro-glyceride,  are  antiseptics  most  commonly  used  by 
dentists  in  the  treatment  of  various  diseased  conditions.* 
In  alveolar  pyorrhoea  Harlan  recommends  hydrogen 
dioxide  and  solution  of  zinc  iodide. 

500.  In  washing  plates  of  artificial  teeth,  regard  must 
be  had  for  their  metallic  character;  for  example,  a  plate 
containing  aluminium  is  said  to  be  affected  by  a  corro- 
sive sublimate  solution  more  readily  than  by  carbolic 
acid. 

A  mouth  wash  containing  i  part  of  corrosive  sublimate 
in  5000  can  be  made  as  follows:  one  grain  of  the  per- 
chloride  of  mercury  and  i  grain  of  chloride  of  ammonium 
to  be  dissolved  in  i  ounce  of  eau  de  cologne,  and  a  tea- 
spoonful  of  the  solution  to  be  mixed  with  two  thirds  of  a 
wineglassful  of  water. 

50 1 .  Experiments  of  M  iller : 

Experiments  were  made  by  Miller  with  various  antisep- 
tics, to  ascertain  which  would  answer  best  to  retard  or  to 
prevent  fermentation  in  the  mouth.  The  following  are 
the  results: 

The  fermentative  action  is 

Prevented         Arrested 
by  1  in  by  1  in 

Corrosive   sublimate 500,000  100,000 

Silver  Nitrate 100,000  50,000 

Iodine  (in  Alcohol) 15,000  6,000 

Iodoform 10,000  5,000 

Naphthalin 9,000  4,000 

Ess.  Oil  Mustard 5,000  2,000 

Permang.  Potassium 2,000  1,000 

Oil  Eucalyptus 600 

*  A  coal  tar  substance  called  creolui  is  claimed  to  exceed  carbolic 
acid  in  deodorizing  efficiency.  Its  exact  chemical  composition  is  a 
trade  secret.     It  is  a  powerful  styptic  and  is  said  to  be  non-poisonous. 


328  DENTAL   CHEMISTRY. 

Prevented  Arrested 

by  I  ill  l.y  1  iu 

Carbolic    Acid i  ,000  500 

Hydrochloric  Acid 1,000  500 

Sodium    Carbonate 200  lOO 

Salicylic  Acid 125  75 

Alcohol,  absol 25  10 

These  results  are  of  considerable  interest  not  only  to 
dentists,  but  also  for  the  preparation  of  efficient  tooth 
powders. 

Miller  claims  to  sterilize  the  mouth,  cavities  in  carious 
teeth,  etc.,  by  the  following  mixture: 

Thymol 4  gJ*. 

Benzoic    Acid 45  gi"- 

Tincture  of  Eucalyptus....   3^-2    fl.    dr. 

Water 25  fl.  oz. 

The  mouth  is  to  be  well  rinsed  with  this  mixture,  es- 
pecially- just  before  going  to  bed,  since  most  of  the  dam- 
age by  fermentative  and  putrefactive  processes  in  the 
mouth  is  done  at  night  during  sleep. 

Miller  has  suggested  a  number  of  formulae,  most  of 
which  contain  eucalyptus;  he  thinks  the  presence  of  cor- 
rosive sublimate  necessary  to  insure  efficiency.  His  mix- 
tures are  intended  to  serve  as  foundations  for  mouth- 
washes, since  many  of  them  are  not  palatable  and  need 
agents  to  be  combined  with  them  which  shall  disguise  the 
burning  taste,  especially  of  thymol  and  of  eucalyptus. 

502.    Deodorizers  :— 

For  fetor  of  the  breath,  etc.,  chlorinated 
Hme  solution,  chlorine  water,  chlorinated 
soda,  permang'anate  of  potassium  solution, 
phenol  sodique  are  used;  also  certain  vegeta- 
ble substances,  as  orris  root.  Various  oils 
such  as  safrol,  oil  of  Pinus  Picea,  oil  of  anise, 


ORGANIC   CHEMISTRY.  329 

oil  of  rose  geranium,  impart  a  pleasing-  frag- 
rance to  the  breath;  a  drop  or  two  in  a  glass 
of  water,  thoroughly  stirred,  is  all  that  is  ne- 
cessary. Many  persons  tire  of  the  taste  of 
the  oils  of  wintergreen  and  of  sassafras.  The 
use  of  orris  has  also  been  carried  to  excess. 
The  author  has  found  Miller's  mouth-wash 
an  excellent  deodorizer. 

503.     Antiseptics  of  more  recent  use. 

Alantol,  C^oHgjO,  liquid,  powerful  internal  antibacterial 
and  antiseptic. 

Alplia-naplithol,  solid,  i  in  10,000  prevents  alcoholic 
fermentation  of  glucose.  (Maximovvitsch).  In  same 
strength  prevents  propagation  of  typhoid  and  tubercu- 
lous bacilli. 

Bctol,  CcH4(0H  )C02.CioH7,  salicylo-beta-naphthylic 
ether,  white  powder,  crystalline;  insoluble  in  water,  solu- 
ble in  boiling  alcohol  and  warm  linseed  oil.     (Robert). 

BisvmtJi  oxyiodidc,  BiOI,  brownish  powder,  insoluble. 
Used  dry.     (Lister,  Reynolds,  and  others.) 

Creolin  already  mentioned,  section  499,  foot  note. 

Cresylic  acid,  said  to  be  superior  in  antizymotic  action 
to  carbolic  acid.     (Dujardin-Beaumetz). 

Iodine  trichloride,  ICI3,  orange-red  powder,  strongl)^  irri- 
tating odor;  i  in  1,000,  in  aqueous  solution,  destroys 
bacillus-spores.     (Riedel). 

Mercuric  albuminate  contains  4  parts  mercuric  chloride 
in  12  of  albumin  and  984  of  milk  sugar. 

Mercuric  Oxycyanide,  said  to  have  six  times  the  bacteri- 
cidal force  of  mercuric  chloride.     (Chibret). 

Oxy-naphtlioic  acid,  alpha.  Said  to  have  five  times  the 
anti-zymotic  action  of  salicylic  acid.  White  microcrys- 
talline  powder  almost  insoluble  in  water,  more  soluble  in 
solutions  of  the  bicarbonates. 


330  DENTAL   CHEMISTRY. 

Sodium  silico-fluoride,  non-toxic,  surgical  antiseptic. 
(Thomson). 

Sodium  sulphite,  benzoated,  non-toxic,  surgical  antiseptic. 
(Heckel). 

Tribrom-phenol,  made  by  action  of  bromine  on  aqueous 
carbolic  acid,  energetic  and  reliable  disinfectant  in  puru- 
lent and  gangrenous  processes.     (Grimm). 

New  Antiseptics  and  Therapeutic  Agents. 

'Aristol,  C20H24O2I2,  a  thymol  derivative,  (page  234:)  light 
chocolate-colored  powder  almost  odorless  and  tasteless, 
used  as  substitute  for  iodoform;  made  by  adding  a  solution 
of  iodine  in  iodide  of  potassium  to  an  aqueous  solution 
of  sodium  hydrate  containing  thymol;  contains  about  46 
per  cent,  of  iodine;  insoluble  in  water  and  glycerin,  slightly 
soluble  in  alcohol,  readily  soluble  in  ether;  is  taken  up  by 
fatty  oils  when  rubbed  up  in  them;  non-toxic. 

Acet07io-resorci?i  is  a  combination  of  two  molecules  of 
resorcin  (page  38)  with  one  of  acetone.  Occurs  in  the  form 
of  small  anhydrous  prisms,  soluble  in  alkalies,  insoluble 
in  water,  alcohol,  ether,  and  chloroform. 

Anisic  add,  C6Hi(OCH3)COOH  is  the  phenol  ester, 
(page  235,)  ofjo-oxybenzoic  acid.  Colorless  prisms,  soluble 
in  alcohol,  insoluble  in  water.     Antiseptic. 

Acetophxnoiie,      phenylmethylketone,     hypnone,     CeH^ 
CO.  — CH3,  (page  235)  is  formed  by  distillation  of  calcium, 
acetate  and  benzoate  in  molecular  proportions,  thus 
(C6H5.COO)oCa+(CH3.COO)2Ca= 
2CaC03+C,H5.CO.CH3. 

Acetal,  diethyl-acetal,  ethylidene  diethyl  ether,  CH3. 
CH(OC2H5)2is  made  by  heating  a  mixture  of  aldehyde 
and  alcohol  to  100°.  It  is  a  colorless,  limpid  liquid,  solu- 
ble in  18  parts  water,  of  agreeable  odor.  Hypnotic. 
(See  class  IV  page  224.) 


ORGANIC    CHEMISTRY.  331 

Alumnolxs  an  aluminium  naphthol-sulphonate,  (page 
237)  occurring  as  a  white  or  pinkish  powder,  very  soluble 
in  water  (with  blue  fluorescence)  and  in  glycerin,  less  so 
in  alcohol  and  in  ether.    Non-irritant,  antiseptic. 

Asaprol,  beta-  naphthol-alpha-mono-sulphonate  of  cal- 
cium, page  237. 

Acetico-tartrate  of  aluminium^  astringent  and  disinfect- 
ant. 

Aluminium  bofoformicate,  astringent,  disinfectant,  slowly 
soluble  in  water. 

Amylene  hydrate,  dimethylethyl-carbinol,  tertiary  amyl 
alcohol  (CH3)2=C(OH),    see  class  II,   p.  223.     Limpid, 

colorless,  hygroscopic  liquid,  of  penetrating  ethereal  odor, 
soluble  in  alcohol,  ether,  chloroform,  and  in  8  parts  water. 
Made  from  amylene,  C5H10,  by  shaking  this  up  with  sul- 
phuric acid  and  subsequently  distilling.  Hypnotic  and 
anodyne. 

Analgen.     See  page  238.     Colorless  crystals. 

/C(OH)\^ 
Atithrarobtn,  desoxyalizarin,  CeH^^     |  ^^CeHg 

^CH  -^""^ 
(0H)2,  page  237.     Yellowish  white  powder,  insoluble  in 
water  and  in  dilute  acids,  soluble  in  glycerin,  in  5  parts 
alcohol,  and  ia  alkaline  media.     Substitute  for  chrysa- 
robin. 

Afiticholerin: — Cholera  antitoxine  solution. 

Antikamnia,  a  white,  micro-crystalline,  odorless,  taste- 
less powder,  nearly  insoluble  in  water,  readily  solu- 
ble in  alcohol  and  ether.  Antipyretic,  analgesic,  and 
anodyne. 

Antinervine^  salicylbromanilid,  salbromalide,  a  mixture 
of  ammonium  bromide,  salicylic  acid,  and  acetanilid. 

Antisepsin,  asepsin,  mono  or   para  bromacetanilid,  (sec 


332  DENTAL    CHEMISTRY. 

page  233.)  Colorless,  prismatic  crystals,  insoluble  in  cold 
water,  slightly  soluble  in  alcohol,  and  in  hot  water. 

Atitithermin,  see  page  233.  White  powder,  insoluble  in 
water.     Antiseptic,  antipyretic,  analgesic. 

Argentamine ,  ethylene-diamine  silver  phosphate,  an  8 
per  cent,  solution  of  silver  phosphate  in  ethylene-diamine 
(see  page  230).  Alkaline  solution  turning  yellow.  Anti- 
septic, astringent,  does  not   coagulate  proteids. 

Benzacetin,  acetamido-methyl-salicylate,  see  page  235; 
white  crystals,  soluble  in  alcohol,  slightly  so  in  water. 
Forms  salts  with  bases.     Antineuralgic. 

Benzanilid,  C4H5.CO.NHC6H5  phenyl-oenzamide,  see 
Class  XIV,  page  232.  Pinkish  white,  crystalline  powder, 
insoluble  in  water,  soluble  in  58  parts  alcohol.  Antipyretic. 

Benzonaphihol,  beta-naphthyl  benzoate,  see  page  237, 
analogous  to  betol  which  is  beta-naphthyl  salicylate  or 
CsH^OHCOOCioH,.  White  crystalline  powder  or  long 
needles;  of  slightly  aromatic  odor,  soluble  in  ether,  chlor- 
oform, hot  alcohol,  almost  insoluble  in  water.  Intestinal 
antiseptic  and  diuretic. 

Benzosol,  C6H4.OCH3.OCOC6H5.  benzoyl-guaiacol,  guai- 
acol  benzoate.  White  aromatic  powder,  soluble  in  chlor- 
oform, ether,  and  hot  alcohol.  Almost  insoluble  in  water. 
Antiseptic,  antitubercular. 

Benzoyleugenol,  colorless,  odorless,  slightly  bitter  crys- 
tals.    Antitubercular. 

Betoly  see  page  237  and  page  307. 

Bismuth  salicylate  (page  235)  basic,  64  per  cent.,  is  used 
as  an  antiseptic  and  disinfectant. 

Bromamide,  mono-brom-phenylacetamide;  crystals  in- 
soluble in  water,  soluble  in  chloroform,  ether,  oils,  and 
boiling  alcohol.     Antipyretic,  analgesic,  etc. 

Bromol,  tribromphenol,  (page  233)  white,  crystalline 
powder  almost  insoluble  in  water.     Disinfectant. 


ORGANIC    CHEMISTRY.  333 

CarvacroL  iodide,  (page  234)  made  from  oil  of  origanum. 
Yellowish-brown  powder,  insoluble  in  water,  used  like 
aristol  and  iodoform. 

Chloralamid,  see  page  224;  colorless,  lustrous,  slightly 
bitter  crystals,  soluble  in  alcohol,  3  parts  glycerin,  slowly 
in  20  parts  water.     Hypnotic. 

Creolin  is  now  said  to  be  an  emulsion  of  carbohydrates 
(?)  from  tar  with  rosin  soap,  or  with  creosol-sulphuric 
acids. 

Creosotal,  creosote  carbonate  is  a  clear  oily  liquid  free 
from  taste  and  odor  of  creosote.     Antitubercular. 

Cresolol,  ortho-,  meta-,  and  para-cresol  salicylates,  pages 
234-235.  Resembles  salol  physically.  Intestinal  anti- 
septic. 

Cresoliodide,  very  light  yellow  powder,  of  disagreeable 
odor,  insoluble  in  water.     Antiseptic. 

Chloral-carbol,  chloral  phenol,  an  oily  liquid,  mixture  of 
equal  parts  chloral  and  carbolic  acid.  For  toothache; 
counter-irritant. 

Chloral-menthol,  equal  parts  chloral  and  menthol;  local 
disinfectant  and  anaesthetic. 

Chloralose,  anhydro-gluco-chloral,  CsHnClsOe,  fine,  bit- 
ter, colorless  needles  soluble  in  warm  water,  slightly  in 
cold.  Anaesthetic,  hypnotic.  Made  by  heating  chloral 
and  glucose. 

Chlorophenol  (see  page  233),  ortho-mono-chlorphenol, 
antiseptic,  volatile  liquid. 

Chloryl,  a  mixture  of  ethyl  and  methyl  chlorides  (see 
page  228),  used  as  anaesthetic. 

Diaphtherin:  a  compound  of  one  molecule  of  orthophe- 
nol-sulphonicacid  (aseptol)  with  two  molecules  of  ortho- 
oxy-quinoline.  A  bright  yellow  powder  readily  soluble 
in  water. 

Dermatol,  C6Hj(OH)3COOBi(OH)2,  is  bismuth  gallate 


334  DENTAL    CHEMISTRY. 

or  subgallate  occurring  as  a  saffron-yellow  powder,  insol- 
uble in  water,  alcohol,  or  ether,  but  soluble  in  dilute  acids. 
Euphofine,  phenyl-urethane,  made  by  interaction  of  ani- 
line and  chlorocarbonic  ethyl  ether.  Occurs  in  crystals 
with  faint  aromatic  odor,  insoluble  in  water,  soluble  in 
alcohol,  strong  and  dilute.     Antipyretic,  etc. 

Europhen,  CeH^.QHg.CHg.OH.CeHj.OH.CHs.-QHs.  di- 
isobutyl  orthocresol-iodide,  an  amorphous  bulky,  yellow 
powder  of  faint  saffron-like  odor,  resembling  iodoform  in 
solubilities. 

Formalin^  a  40  per  cent  aqueous  solution  of  formaldehyde 
HCO.H,  said  to  be  a  non-poisonous  antiseptic  of  great 
power.  Formaldehyde  is  made  by  leading  a  mixture  of 
gaseous  methyl  alcohol  and  air  over  gently-heated  copper 
oxide,  and  carefully  fractioning  the  liquid.  It  is  a  gas  of 
pungent  odor. 

J/yr/^/ (section  384)  is,  according  to  Harlan,  an  excel- 
lent antiseptic  in  infected  root  canals.  It  is  a  volatile  oil 
containing  various  terpenes,  cineol  (eucalyptol),  and  a 
camphor-like  substance. 

Potassiu7n-sodium,  a  preparation  of  these  metals  in  para- 
fifin  inserted  into  cavities  for  cleansing  purposes,  hy- 
droxides being  formed,  and  saponification  taking  place. 

Pyrozone  is  a  name  given  to  accurate  percentage  solu- 
tions of  hydrogen  dioxide  which  is  now  obtained  absolute. 

The  three  solutions  of  pyrozone  on  the  market  are 
the  3  per  cent,  aqueous,  the  5  per  cent,  ethereal,  and  the 
25  per  cent,  ethereal.  The  3  per  cent,  may  be  used  freely 
as  a  mouth  wash  especially  for  habitual  smokers.  The  5 
per  cent,  solution  is  a  powerful  antiseptic  and  a  bleacher 
of  teeth,  as  is  also  the  25  per  cent.  The  25  per  cent,  solu- 
tion is  used  in  pyorrhoea  alveolaris;  it  is  a  caustic. 

Salol  (section  441)  is  used  in  dentistry  as  a  root  filling, 
when  liquefied  by  heat. 


ORGANIC    CHEMISTRY.  335 

Silver  ?iitrate  {section  175)  is  now  used  in  dentistry  in 
10  per  cent,  solution,  or  weaker,  in  pyorrhoea  alveolaris.* 

Sodium  ethylate,  CaHs.ONa,  is  obtained  by  dissolving 
sodium  in  alcohol,  and  evaporating  the  solution  in  a 
stream  of  hydrogen.  It  is  a  colorless,  hygroscopic  sub- 
stance rapidly  absorbing  carbon  dioxide  from  the  air,  and 
immediately  decomposed  by  water.  Liquor  sodii  ethylatis  is 
a  solution  of  19  per  cent,  of  sodium  ethylate. 

It  is  used  as  a  caustic  for  overhanging  gums. 

Sodium fluosilicate,  NaaSiFe,  also  called  sodium  silico- 
fluoride  is  prepared  by  neutralizing  hydrofluosilicic  acid 
with  sodium  hydrate  or  carbonate.  According  to  Harlan 
it  is  especially  valuable  as  a  sterilizer.  It  is  not  very 
soluble  in  cold  water.  In  medicine  it  is  known  as 
"salufer." 

Stdpho-carbolates : — The  sulpho-carbolate  of  zinc  is  used 
widely  as  an  antiseptic,  especially  in  typhoid  fever. 

Trichloracetic  acid,  (section  426)  is  also  used  in  dilute 
solutions  as  an  injection  around  roots  of  teeth  to  dissolve 
minute  particles  of  calculi. 

Other  newer  antiseptics,  solids,  soluble  in  water:  — gal- 
lobromol,  C6Br2(OH)3CO.OH,  dibromgallic  acid;  iodine 
trichloride,  ICI3;  lactol  (beta-naphthol  lactate);  lactophe- 
nin  (lactyl-phenetidin);  lysol;  picrol;  sodium  chloro- 
borate;  sodium  dithiosalicylate;  sodium  formate;  sodium 
paracresotate;  sodium  sulpho-salicylate;  sodium  tetra- 
borate. 

Other  new  antiseptics,  solids,  only  slightly  soluble  in 
water  are  camphoric  acid,  C8Hi4(CO.OH)2;  diaphthol; 
hydracetine  (pyrodine,  acetyl  phenyl  hydrazide),  (page 
233);  hydroquinone,  C6H4(OH)2,  page  234;  loretin,  C9H4N. 
I.OH.SO3H,  meta-iodo-ortho- oxy - quinoline-ana - sulph - 
onicacid.  Losophan,  C6H.I3.OH.CH3:  tri-iodo-meta-cresol. 

•J.  E.  Craven. 


336  DENTAL    CHEMISTRY. 

Salacetol,  C,H,^^^^-^^''^^^^'  salicyl-acetol; 

phenylacetic  acid,  CeHs.CHj.COaH,  alpha-toluic  acid. 

Other  new  antiseptics,  solids,  insoluble  in  water  are 
cresalol,para — ,C6H4.0H.COO.C6H4.CH3,paracresol  salicy- 
late; di-iodoform,  ethylene  periodide,  tetra-iodo-ethy- 
lene;  europhen,  CeHa.CiHg.CHa.OH.CeHa.OH.CHs.QHg, 
di-isobutylorthocresol  iodide;  hydronaphthol;  iodo- 
eugenol;  iodo-phenacetine  (iodo-phenine);  sulphaminol 
(thio-oxy-diphenyl-amine);  thioform  (basic  bismuth 
dithiosalicylate);  thio-resorcin;  piperonal  (heliotropin). 

Other  new  antiseptics  in  liquid  form  are  formaline; 
phenosalyl  (a  mixture  of  carbolic,  salicylic,  and  benzoic 
acids  dissolved  in  lactic  acid);  tricresol;  tricresolamine,  a 
mixture  of  equal  parts  ethylene  diamine  and  tricresol,  used 
in  4  per  cent,  solution;  kresin,  a  solution  of  cresylic  acid 
in  solution  of  sodium  cresyloxy-acetate;  lysol,  a  50  per 
cent,  solution  (saponaceous)  of  cresols;  resol. 

New  antiseptics  used  in  treatment  of  tuberculosis: — 
cinnamic  acid;  phenyl-acetic  acid;  benzosol  CeH^.OCHg. 
OCOCeHs,  benzoyl-guaiacol;  benzoyleugenol;  chloroph- 
enol;  creasotal,  creasote  carbonate;  oleo-creasote;  oleo- 
guaiacol;  eucalyptol;  guaiacol  ( methyl-pyrocatechol); 
guaiacol  biniodide;  guaiacol  carbonate;  guaiacol  salicy- 
late (guaiacol-salve);  styracol  (cinnamyl  guaiacol). 

Various  other  antiseptics  or  disinfectants  are  cresapol; 
listol  (compound  of  thymol  and  iodine);  iodocasein;iodo- 
formin,  a  derivative  of  formaldehyde;  malakin  (salicyl- 
aldehyde  paraphenetidin) ;  sapocresol;  solphinol  (borax, 
boric  acid,  alkaline  sulphites.)  Volkmann's  antiseptic 
liquor  is  said  to  be  a  solution  of  thymol  in  a  mixture  of 
alcohol,  glycerin,  and  water. 

Boro-lyptol  is  the  namQ  given  to  an  antiseptic  said  to 
contain  5  per  cent,  aceto-boro-glyceride,  and  o.i  percent. 


ORGANIC    CHEMISTRY.  337 

formaldehyde  in  combination  with  active  antiseptic  con- 
stituents of  pinus  pumilio,  eucalyptus,  myrrh,  storax, 
and  benzoin. 

New  local  ancBsthetics  are  erythrophleine  hydrochlorate 
and  eugenol-acetamide,  both  soluble  in  water.  Pental 
(tri-methyl-ethylene)  is  an  anaesthetic. 

Pyoctanin,  yellow,  is  used  in  dentistry  in  gingivitis, 
phagedenic  pericementitis,  and  as  an  injection  into  salivary 
cysts.     It  is  a  local  analgesic. 

A  new  dental  anodyne  called  odo?itodol  is  said  to  be  a 
mixture  of  cocaine  hydrochlorate,  cherry  laurel  oil,  tinct- 
ure of  arnica,  and  solution  of  ammonium  acetate. 

New  hypnotics  are  acetal,  (ethylidene  diethyl  ether); 
acetophenone;  artiylene  hydrate;  antispasmin;  chloral- 
amid;  chloral-ammonium;  hyoscine;  hypnal;  hypnone; 
methylal;  narceine;  thymacetin;  trional;  uralium;  ure- 
thane. 

New  antipyretics:  — acetanilid  (antifebrin);aceto-ortho- 
toluid;  anisic  acid;  antikamnia;  Entinervin  (salicyl  broma- 
nilid);  antisepsin  (mono  or  para  bromacetanilid);  antith- 
ermin  (phenyl  hydrazin  levulinic  acid);  asaprol;  benz- 
anilid;  bromamide  (mono-brom-phcnyl-acetate);  chinol 
(quinoline  monohypochlorite);  euphorin;  formanilid; 
hydracetine;  hydroquinone;  lactophenin;  methacetin; 
neurodin;  phenacetin;  salocoll;  sodium  paracresotate; 
thermodin;  tolypyrin. 

New  analgesics  are  acetanilid;  antikamnia;  antinervin; 
bromamide;  chloral-caffeine;  euphorin;  exalgin;  for- 
manilid: hypnal;  j  phenacetin;  quinal<Ten;  salipyrine; 
agathin;  antikol;  antithermin;  asepsin. 

New  ifitestinal  ajitiseptics  or  disinfectants,  are  benzonaph- 
thol;  betol;  bismuth  beta-naphtholate  and  salicylate; 
bismuth  tribromphenol;  bromol;  cresalol,  para-guaiacol 
salicylate;  hydronaphthol;  lactol  (beta-naphthol  lactate); 


338  DENTAL    CHEMISTRY, 

salacetol;  sodium  parac-resotate;  zinc  sulphocarbolate. 
New  diuretics  are  asparagin;  benzonaphthol;  diuretin 
(sodio-theobromine  salicylate);  scillipicrin;  scoparine; 
symphorol  (caffeine  sulphonate  nasrol);  uropherin  (lith- 
ium diuretin). 

Uric-solvents  not  hitherto  mentioned  are  tartarlithine, 
piperazine  (page  230),  lycetol  (dimethyl-piperazine- 
tartrate),  lysidin,  tetra-ethyl-ammonium  hydroxide  (10 
per  cent,  solution). 

Tartarlithine  (the  lithium  analogue  of  cream  of  tartar) 
is  used  as  an  antilithic  to  combat  the  morbific  element  in 
pyorrhoea  alveolaris  which,  according  to  Drs.  C  N.  Pierce 
and  E.  C  Kirk,  is  uric  acid  in  combination  forming  urates. 

New  mouth  washes: — 

Borine  is  a  liquid  said  to  contain  the  active  constituents 
of  benzoin,  winter  green,  meadow-sweet,  golden  rod,  and 
witch  hazel  with  stearoptens  of  wild  thyme,  eucalyptus, 
and  peppermint,  with  boracic  acid;  glycothymolijie  is  a 
liquid  said  to  contain  sodium  (?)  borax,  benzoin,  salicylic 
acid,  eucalyptol,  thymol,  menthol,  oil  of  gaultheria,  oil  of 
pinus  pumilio,  glycerin,  and  solvents. 
Miscellaneous, 

Traumatol  is  an  iodocresol  of  purple  red  color,  substi- 
tute for  iodoform. 

Stypticitie  is  the  hydrochlorate  of  cotarnine,  used  in  con- 
trolling menstrual  haemorrhages. 

Eudoxin  is  said  to  be  the  bismuth  salt  of  nasophen,  or 
tetraiodophenolphthalein. 

Hypnoacetiji  isacetophenonacetyl-paramidophenol  ether. 

Urotropin  is  a  hexamethylene  tetramine  (CH2)6N4 

Benzoinol,  Oleum  Petrolatum  Benzoinat,  is  a  benzoated 
petroleum  product  used  as  vehicle  for  camphor,  cocaine, 
carbolic  acid,  etc. 

Blancoline,  is  a  perfectly  white,  odorless,  and  neutral 
petroleum  jelly. 

Terraline  is  the  name  of  a  special  petroleum  jelly. 
Vasogen,  oxygenated  vaselin,  sulpholeated  mineral  oil 
miscible  with  water,  used  as  vehicle. 


THE  TEETH  AND  THE  SALIVA.  339 


CHAPTER  V. 


THE  TEETH  AND  THE  SALIVA. 


504.  Structure:  the  chief  mass  of  a  tooth 
consists  of  a  substance  called  dentine,  in  the  in- 
terior of  which  is  the  pulp  cavity.  The  crown 
of  the  tooth  is  invested  by  a  substance  called 
enamel,  which  extends  some  distance  down 
the  neck,  but  the  fangs  are  covered  by  a  sub- 
stance known  as  cement  {crnsta  petrosa). 
Before  describing"  the  dental  tissues  further, 
we  shall  pay  attention  for  a  moment  to  the 
chemistry  of  bone. 

505.  Bone  consists  of  an  organic  substance  called  os- 
scin,  which  we  have  seen  is  a  proteid  substance  belonging 
to  the  collagens,  intimately  combined  with  a  mineral 
substance  called  bone  earth,  in  proportion  of  about  30  of 
ossein  to  70  of  bone  earth.  The  latter  is  a  mixture  of 
various  salts,  as  calcium  phosphate,  calcium  carbonate, 
calcium  fluoride,  and  magnesium  phosphate,  of  which  the 
most  abundant  in  quantity  are  the  calcium  phosphate  and 
carbonate.     Bone  contains  also  water  and   fat.     The  os- 


340  DENTAL   CHEMISTRY. 

sein   of  bone    resembles  gelatin,    and  by  boiling  ossein 
with  water  it  is  changed  into  gelatin. 

Hoppe-Seyler  gives  the  general  composition  of  normal, 
undried  bone  as: 

Water 50.00  per  cent 

Fat 15.75     "       " 

Ossein 11.40     "       •' 

Bone   earth 21.85     " 

Most  of  the  water  is  combined  in  the  ossein.  Express- 
ing the  composition  of  bone  in  order  to  show  the  relative 
percentage  of  organic  and  inorganic  substances  we  find 
it,  according  to  Heintz,  as  follows: 

Inorganic  substances. . . .  69.53  to  68.88 

Organic   substances 30.47  '*  31.12 

Analysis  of  the  ash  shows  that  of  the  inorganic  sub- 
stances tribasic  calcium  phosphate,  Ca3(P04)2,  constitutes 
from  83.89  to  87.70  per  cent.,  calcium  carbonate  8.9  to  13, 
03,  tribasic  magnesium  phosphate,  1.04  to  1.70  per  cent., 
calcic  fluoride  and  chloride,  0.76  to  4.90  per  cent.  Berze- 
lius's  analysis  of  bone  resulted  as  follows:    . 

Ossein 32.17 

Calcium  phosphate 5 1 .04 

"     « fluoride 2.00 

"       carbonate 1 1 .30 

Soda  with  sodic  chloride 1.20 

Magnesium  phosphate 1.16 

Vessels i .  1 3 

506.  The  inorganic  constituents  of  bone  increase 
slightly  with  age  and  the  bone  becomes  more  porous. 
The  marrow  of  bones  is  of  different  composition,  accord- 
ing to  locality,  but  in  the  long  bones  (yellow  marrow)  is 
96  per  cent,  fat,  with  some  cholesterin,  hypoxanthin, 
albumin  and,  occasionally,  lactic  acid.  Red  marrow  con- 
tains a  small  proportion  of  fat,  much  albumin  and  salts, 
and   an    acid    resembling    lactic    acid.     In    diseases   of 


THE  TEETH  AND  THE  SALIVA.  341 

bone  the  inorganic  salts  change  in  quantity,  and  the  or- 
ganic constituents  in  quality. 

ANALYSIS  OF  BONE  IN  CARIES  OF  VERTEBRA. 

Calcium  phosphate 33-91 

"       carbonate 7.60 

Magnesium  phosphate 1.93 

Soluble  salts,  chiefly  NaCl..  0.61 

Ossein,  etc 19-58 

Fat 1.22  (Valentin). 

ANALYSIS  OF  BONE  IN  NECROSIS. 

Calcium  phosphate,  etc 72.63 

Calcium  carbonate 4. 03 

Magnesium  phosphate 1.93 

Soluble  salts O.61 

Ossein 19-58 

Fat 1.22 

507.  Turning-  now  to  the  chemical  constitu- 
tion of  the  teeth,  we  find  that  the  cement  has 
a  structure  resembhng;  bone,  and  its  chemi- 
cal composition  is  almost  the  same,  namely 
organic  substances  30  parts,  inorganic  70 
parts;  of  the  latter  nearly  65  parts  of  the  70 
are  composed  of  f>hospJiates  of  calcium  and 
magnesium  and  carbonate  of  calcium,  as  fol- 
lows: 

Calcium  phosphate  ....  60.7 
Magnesium  phosphate.  .  1.2 
Calcium  carbonate 2.g(Bibra). 

508.  The  enamel  of  teeth  is  nearly  all  inor- 
ganic matter;  in  the  enamel  of  some  animals, 
as  the  dog,  there  seems  to  be  no  organic  mat- 


342  DENTAL   CHEMISTRY. 

ter  at  all.  In  man,  on  an  average,  the  inor- 
ganic constituents  are  from  95  to  97  per  cent, 
in  amount,  the  organic  from  5  to  3;  in  the 
teeth  of  young  infants,  however,  the  inorganic 
matter  is  only  from  77  to  84  per  cent. 

AVERAGE  COMPOSITION  OF  THE  ENAMEL. 

Water  and  organic  substances 3.6 

Calcium  phosphate  and  fluoride 86.9 

Magnesium  phosphate 1.5 

Calcium  carbonate 8.0 

hoppe-seyler's  analysis. 

Calcium  carbonate   and   phosphate,  Cajo 

C03,6P04 96.0 

MgHP04  (neutral  phosphate  of  magne- 
sium ) 1 .05 

Organic  substances 3.60 

509.    The  dentine  is  more  like  bone  than  the 

enamel  is,   but   less  like  it  than  the  cement. 

It  is  composed  of  animal  matter  impregnated 

with  earthy  salts.     It  averages  from  26  to  28 

per  cent,  organic  substances  to  .74  to  72    of 

inorganic  matter. 

analysis  of  dentine. 

Woman.  Man. 

Organic   matter — ossein  and  ves- 
sels    27.61     20.42 

Calcium  phosphate 66.72    67.54 


THE  TEETH  AND  THE  SALIVA.  343 

Analysis — Contmued. 

Calcium  carbonate 3.36  7.97 

Mag^nesium  phosphate 1.08  2.49 

Other  salts  (NaCl,  etc.) 083  i.oo 

Fat 0.40  0.58 

ANALYSIS   OF  HOPPE-SEYLER. 

CaioCOg,  6PO4 72.06 

iMgHP04 0.75 

Organic  substances 27.70 

The  organic  matter  of  the  dentine  resembles  the  ossein 
of  bone,  but,  according  to  Hoppe-Seyler,  the  walls  of  the 
canaliculi  are  invested  with  a  body  resembling  keratin  or 
clasticin.  [Keratin  is  a  proteid  substance  and  is  the  chief 
component  of  epidermic  structures.  It  is  noticeable  for 
the  large  amount  of  sulphur  it  contains.  It  is  closely  re- 
lated to  albumin,  yielding  leucin  and  tyrosin  when 
decomposed.  Its  percentage  composition  is  C=50  to  5 1.6, 
H=6.4to7.2,N  =  16.2  to  17.9,  S=07  to  5.0,  O=20to  22.4. 
It  is  insoluble  in  alcohol  and  ether,  swells  up  in  boiling 
water,  and  is  soluble  in  the  caustic  alkalies.  It  is  not  lia- 
ble to  decomposition,  and  melts  when  heated. 

Elasticin  is  related  to  keratin,  and  is  the  substance  com- 
posing the  fibres  of  yellow  elastic  tissue.  It  is  sometimes 
called  elastin.  It  yields  leucin  but  not  tyrosin.  Its  per- 
centage composition  is  C  =  54.32,  H  =  6.99,  N  =  16.75, 
ash  =  0.5]. 

Dentine  contains  4  per  cent,  less  water  than  bone.  Its 
specific  gravity,  according  to  C.  Krause,  is  2.080.  The 
walls  of  the  canaliculi  do  not  yield  gelatin,  but  the  ground 
substance  of  dentine  may  be  transformed  into  gelatin, 
when  heated  in  a  Papin's  digester.  The  globules  of 
dentine  are  not  convertible  into  gelatin,  and  resist  the 
action  of  acids  better  than  any  other  portions  of  the  tis- 
sue do. 


344  DENTAL   CHEMISTRY. 

Of  the  three  substances  of  which  the  teeth  are  com- 
posed we  find  that  the  enamel  is  the  hardest,  the  dentine 
next,  and  the  cement  the  least.  The  enamel  is  hard  and 
brittle. 

If  the  enamel  be  treated  with  dilute  hydrochloric  acid 
the  calcium  phosphate  is  dissolved,  and  there  remain  pris- 
matic fibres  which  resemble  epithelium  and  are  not  at- 
tacked by  boiling  water.  If  the  cement  be  treated  with 
an  acid,  its  inorganic  constituents  are  dissolved  and  there 
remains  an  organic  residue  which  is  said  by  Hoppe-Se\'ler 
not  to  yield  gelatin;  [according  to  some  authors  this  sub- 
stance does  yield  gelatin].  If  the  dentine  be  treated  with 
acids,  organic  matter  is  left,  most  of  which  yields  gelatin, 
but  some  does  not.  According  to  Bibra,  molar  teeth  ao- 
pear  to  contain  more  mineral  matter  than  incisors. 

510.     Various  analyses  (tabulated  for  reference). 

CEMENT  OF  TOOTH. 

Of  OX  (Fremy).  Of  man  (Bibra). 

Ash  (containing  an  average  of)  67.1    per 

cent 70.58  per  cent. 

Calcic    phosphate 60.70        " 

Magnesic i  .20        " 

Carbonate  of  lime 2.90        " 

DENTINE  OF  TOOTH,  (hOPPE-SEYLER  ). 

CaioCOa.  6(P04) 72.06 

MgHPO, 0.75 

Organic  substances 27.70 

DENTINE  (bibra). 

Adult  woman.    Adult  man. 

Organic  matter,  ossein  and  vessels..  ,  27.61  20.42 

Phosphate  of  lime 66.72  67.54 

Carbonate      "         3.36  7.97 

Phosphate  of   magnesia 1.08  2.49 

Other  salts  (XaCl,  etc.) 0.83  i.OO 

Fat 0.40  0.58 


THE  TEETH  AND  THE  SALIVA.  345 

ENAMEL  OF  TOOTH. 

Water  and  organic  substances 3.6 

Calcic  phosphate  and  fluoride 86.9 

Magnesic  phosphate 1.5 

Calcic  carbonate 8.0 

It  is  thus  given  by  Hoppe-Seyler: 

Cai„C(33  6(  PO,) 96.00 

MgHPO, 1.05 

Organic  substances 3.60 

ENAMEL  AND  DENTINE  COMPARED — OX  (aEBY). 

Enamel.       Dentine. 

Organic  substances  and  water...,      3.60       27.70 
Inorganic         "  96.40       72.30 

In  100  parts  ash — 

Calcic  phosphate 93-35  91-32 

"       carbonate 4.80  1.61 

"       oxide 0.86  5.27 

Magnesic  carbonate O.78  0.75 

Calcic  sulphate o.  12  0.09 

Oxide  of  iron 0.09  o.io 

DENTINE,  CEMENT,  AND    ENAMEL    COMPARED. 

Calcium        Magnesium  Calcium 

Ash.  Phosphate.      Phosphate.        Carbonate. 

Dentine 76.8  70.3  4.3  2.2 

Cement 67.1  60.7  1.2  2.9 

Enamel 96,9  90.5  traces.         2.2 

Minute  amounts  of  chlorine  and  fluorine  are  found,  es- 
pecially in  the  enamel.     (Fremy.) 

CEMENT  AND  DENTINE  COMPARED,  (aEBY). 

Cement.  Dentine. 

Calcium  phosphate 61.32  63.35 

"        oxide 5.27  0.86 

'•        carbonate 1.61  4.80 

•'       sulphate 0.09  0.12 


346  DENTAL   CHEMISTRY. 

Cement — Continued. 

Magnesium  carbonate b.75  0.78 

Ferric  oxide o.  10  0.09 

Organic  substances 27.70  26.00 

ANALYSIS    OF  TEETH  BY   BERZELIUS. 

Organic  matter 28.0 

Calcium   phosphate 64.4 

Magnesium  phosphate i.o 

Calcium  carbonate 5.3 

Sodium  "         and  chloride 1.3 

Water,  animal  matter,  alkali  (traces) 0.0 


1 00.0 

511.  Action  of  y carious  Substances  on  the 
Teetli:- 

Owing  to  the  solubility  in  acids  of  the  phos- 
phates and  carbonates  of  magnesium  and  cal- 
cium, it  stands  to  reason  that  a  g:reat  part  of 
tooth  structure  may  be  destroyed  when 
brought  into  contact  with  substances  either 
themselves  acid  or  of  strongly  acid  reaction. 

According  to  many  authorities  as  Westcott,  Allport, 
Mantegazza,  Magitot,  Leber  and  Rottenstein,  etc.,  the 
strong  mineral  and  vegetable  acids  act  promptly  upon  the 
teeth.  Leber  and  Rottenstein  found  that  in  time  a  solution 
of  tartaric  acid,  i  in  1000  attacked  the  enamel,  as  did  also 
crushed  grapes,  or  a  i  in  1000  solution  of  acetic  acid,  of 
oxalic  acid,  or  i  in  100  solution  of  alum,  or  i  in  1000  of 
lactic  acid.  According  then  to  Leber  and  Rottenstein,  as 
also  to  Westcott,  Allport,  and  Mantegazza,  all  the  vege- 
table acids  without  distinction  attack  the  enamel  of  the 
teeth.  It  is  well  to  bear  in  mind  such  substances  in  daily 
use  as  are  either  acids  or  have  an  acid  reaction,  and 
hence  should  not  be  allowed  to  come  constantly  into  con- 


THE  TEETH  AND  THE  SALIVA.  347 

tact  with  the  teeth;  these  are  the  mineral  acids,  2i?,  sul- 
phuric, nitric,  hydrochloric,  phosphoric,  etc.,  the  vegetable 
acids,  as  oxalic,  acetic,  tartaric,  lactic,  benzoic,  salicylic, 
tannic,  etc,,  many  compounds  of  the  metals,  as  ferric  chlo- 
ride ("tincture  of  iron"),  acid  phosphates  of  calcium, 
magnesium,  etc.,  etc.,  alum,  arsenic,  corrosive  sublimate, 
zinc  chloride,  cream  of  tartar  (acid  potassium  tartrate), 
the  sulphate  and  subsulphate  of  iron,  chromic  anhydride 
(chromic  "acid"  so-called).  Solutions  of  hydrogen  diox- 
ide are  acid  in  reaction;  some  preparations  of  it  contain 
much  less  acid  than  others. 

C.  A.  Brackett  has  examined  a  number  of  substances 
used  in  dentistry  and  finds  the  following,  among  many 
other  substances,  to  be  acid  in  reaction: 

Ordinary  alcoholic  tincture  of  myrrh  (the  specimen  was 
some  months  old). 

A  solution  of  i  part  chloride  of  zinc  to  2  parts  glycer- 
ine. 

Glycerine,  2  parts,  tincture  of  aconite  root,  i  part. 

He  found  also,  as  might  be  expected,  that  the  liquid 
portion  of  various  "cements"  was  acid  in  reaction. 

Among  substances  but  feebly  acid  in  reaction  may 
be  mentioned  boracic  acid. 

Among  substances  which,  if  pun,  should  be  neutral  in 
reaction  we  find  silver  nitrate,  carbolic  acid.  Among  ar- 
ticles of  diet  which  tend  to  attack  the  teeth  may  be  men- 
tioned acidulated  drinks,  foods  readily  becoming  acid, 
and  saccharine  articles,  shown  by  Miller  to  be  converted 
into  lactic  acid. 

512.  Chemistry  of  caries:  three  theories  have  been 
advanced  to  account  for  caries,  namely,  the  chemical 
theory,  the  vital  theory,  and  tJie  germ  theory.  According  to 
the  chemical  theory,  the  substance  of  the  tooth  is  de- 
composed by  an  acid;    this  acid  acts  more  readily   on 


348  DENTAL    CHEMISTRY. 

dentine  than  on  enamel,  hence  the  tendency  to  the  en- 
largement of  the  cavity  toward  the  internal  portions  of 
the  tooth.  The  origin  of  the  acids  thus  supposed  to  pro- 
duce caries  has  been  a  subject  of  much  inquiry.  For  a 
time  the  saliva  was  supposed  to  furnish  them,  but  it  was 
shown  that  decay  occurred  in  mouths  in  which  the  saliva 
was  habitually  normal,  and  did  not  occur  in  some  mouths 
in  which  the  saliva  was  habitually  acid.  (Black).  The 
hypothesis  that  the  acid  is  furnished  on  the  spot,  through 
the  decomposition  of  the  food,  seems  much  more  feasible, 
and  the  production  of  the  acid,  if  coming  through  fermen- 
tation, decomposition,  or  remoleculization  of  the  sub- 
stances lodged  about  the  teeth,  makes  it  easy  for  one  to 
"glide  from  the  old  acid  theory  to  the  new  germ  theory." 
(Black). 

The  germ  theory  of  caries  sets  forth,  according  to 
Miller,  that  no  less  than  five  different  fungi  exist  in  car- 
ious human  teeth.  These  fungi  have  the  power  of  caus- 
ing fermentation  in  solutions  containing  fermentable  car- 
bohydrates and  producing,  as  one  of  the  products,  opti- 
cally inactive  lactic  acid.  Free  oxygen  is  not  required  for 
the  production  of  this  fermentative  action,  though  it  is 
probably  accessory  to  the  life  and  growth  of  the  fungi. 
They  have  the  power  to  invert  sugar,  that  is,  to  convert 
infermentable  cane  sugar  into  fermentable  glucose. 
When  sound  teeth  are  exposed  to  the  action  of  these 
fungi,  they  are  rapidly  deprived  of  lime,  and,  on  micro- 
scopic examination,  large  masses  of  bacteria  will  be  found 
in  the  dental  channels.  The  equation  for  the  production 
of  the  lactic  acid  has  already  been  given. 

The  vital  theory  supposed  caries  to  result  from  an  in- 
flammation of  the  structure  of  the  dentine,  terminating  in 
the  final  breaking  down  of  the  part;  and  as  the  structure 
is  incapable,  as  is  well  known,  of  physiological  repair,  a 
cavity  is  the  inevitable  result.     According  to  Black,  it  is 


THE  TEETH  AND  THE  SALIVA.  349 

still  very  uncertain  whether  any  of  the  theories  in  regard 
to  caries  are  correct,  but  the  phenomena  are  explained  by 
more  than  one  with  sufficient  accuracy  to  be  of  great 
value,  both  in  the  prevention  and  treatment.  Whatever 
may  be  the  theories,  it  is  claimed  that  the  teeth  deteriorate 
as  an  effect  of  mental  overwork;  among  the  hard-worked 
pupils  of  the  Paris  public  schools,  the  teeth  become  deter- 
iorated in  a  few  weeks  after  entry.  According  to  Parker, 
increased  decay  and  increased  sensibility  of  the  dentine 
are  apparent  in  men  training  for  athletic  trials.  Williams 
has  shown  that  any  mental  strain  shows  itself  in  the 
teeth  in  a  short  time. 

THE   SALIVA. 

513.  The  Saliva:  the  saliva  is  the  product 
of  the  combined  secretion  of  the  parotid, 
submaxillary,  and  sublingual  glands.  In  the 
mouth  these  secretions  are  mixed  together, 
and,  also  with  it  the  mucus  secreted  in  the 
oral  cavity. 

Physical  characteristics  of  mixed  saliva: 
taste,  none;  color,  none;  odor,  none;  specific 
gravity,  1002  to  1006;  reaction,  alkaline;  ap- 
pearance,  generally  turbid;  consistence,  glairy, 
viscid,  frothy.  On  standing  for  some  hours 
in  a  cylindrical  glass  vessel,  an  opaque,  whit- 
ish deposit  collects  at  the  bottom,  while  the 
supernatant  fluid  becomes  clear  and  of  a  faint, 
bluish  tinge. 

The  average  daily  amount  excreted  has 
been  placed  at  1500  grams  (about  three  pints); 
according  to  Ralfe  this  is  probably  too  high. 


350 


DENTAL    CHEMISTRY. 


and  800  to  900  grams  (less  than  a  quart)  is 
nearer  the  mark. 

The  specific  gravity,  according"  to  some 
authors,  may  range  normally  as  hig:h  as  1009. 
Saliva  from  different  individuals  may  show  a 
constant  difference  in  alkalinity,  but  it  varies 
only  within  narrow  limits,  and,  while  showing" 
within  certain  limits  in  the  same  individual  a 
constant  degree  of  alkalinity,  there  is  a  decid- 
ed and  constant  difference  in  different  individ- 
uals, but  no  constant  corresponding  difference 
in  diastatic  action,  according  to  Chittenden. 
(Charles).  The  solids,  present  in  saliva,  form 
only  about  one  half  of  one  per  cent,  of  it;  half 
nearly  of  these  solids  are  salts,  the  rest  pro- 
teids,  namely  ptyalin,  globulin,  and  serum  al- 
bumin. 

The  alkalinity  would  seem  to  depend  on  the 
presence  of  alkaline  bicarbonates  and  phos- 
phates with,  possibly,  help  from  a  combination 
of  the  ptyalin  with  soda.  The  sediment  con- 
sists of  epithelial  cells  and  salivary  corpuscles 
— the  latter  resembling  the  colorless  blood 
corpuscles  and  probably  derived  therefrom  ; 
under  the  microscope,  they  present  the  same 
appearance  as  lymph  cells,  which  have  become 
swollen  in  water  and  within  their  bodies,  as 
long  as  they  are  uninjured,  a  lively  movement 
of  small  molecules  may  be  perceived. 

514  Chemical  composition  of  saliva:  the  most  import- 
ant constituents   of  saliva  are  the  diastatic  ferment   or 


THE  TEETH  AND  THE  SALIVA.  351 

ptyalin,  as  it  is  called,  imicin,  and  the  chlorides  of  sodium 
and  potassium;  in  addition  are  found  traces  of  albumin, 
fat,  potassmm  sidphocyanide,  sulphates  and  phosphates  of 
the  alkalies  and  alkaline  earths,  chiefly  calcium  phos- 
phate, also  calcium  carbonate,  and  oxide  of  iron.  Some- 
times, even  in  normal  saliva,  urea  and  ammonium  nitrite 
are  found.  Saliva  contains  small  quantities  of  nitrogen 
and  oxygen,  and  an  abundance  of  carbonic  acid.  The 
following  are  analysis  of  the  mixed  saliva: 

FRERICHS. 

Water 994. 10 

Solids 5.90 

Epithelium  and  mucus 2. 13 

Fat 0.07 

Mucin  and  traces  of  alcoholic  extract 1.41 

Potassium  sulphocyanide O.io 

Chlorides  of  sodium  and  potassium,  phos- 
phates of  sodium,  potassium,  and  oxide 
of   iron 2. 19 

JACUBOWITSCH. 

Water 99-5 1 

Solids 0.48 

Soluble  organic  bodies,  ptyalin,  etc 0. 130 

Epithelium 0. 160 

Inorganic  salts O.182 

Potassium  sulphocyanide 0.006 

Potassium  and  sodium  chloride 0.084 

SIMON. 

Water 991 .22 

Solids 8.78 

Ptyalin 4.37 

Mucin 1.40 

Sulphocyanide 1.40 

Salts 1 .40 


352  DENTAL   CHEMISTRY. 

BERZELIUS. 

Water 992-9  ■ 

Solids 7.1 

Ptyalin 2.9 

Mucin 1.4 

Sulphocyanide 1.4 

Salts 1 .9 

HAMMERBACHER. 

Water 92.42 

Solids 0.58 

Epithelium  and  mucin 0.220 

Ptyalin  and  albumin 0.140 

Inorganic  salts 0.220 

Potassium  sulphocyanide 0.004 

IN   100    PARTS  SOLIDS. 

Epithelium  and  mucin 37-98 

Ptyalin  and  albumin 23.97 

Inorganic   salts 38-03 

IN   100  PARTS  ASH. 

Potash 45-71 

Soda 9.59 

Lime 5.01 

Magnesia 0.16 

Phosphoric  anhydride 18.85 

Sulphuric              "       6.38 

Chlorine 18.35 

Enderlin  gives  in  the  100  parts  ash  92.37  as  soluble  and 
5.51  as  insoluble,  of  which  sodium  chloride  (common 
salt)  =  61.93,  sodic  phosphate  =  28.12,  calcium  phos- 
phate and  carbonate  =  5.51,  and  sodium  carbonate  =  2. 31. 

The  functions  of  the  saliva  are  mechanical  and  chemi- 


THE  TEETH  AND  THE  SALIVA.  353 

cal:  fats  are  feebly  emulsified  and  soluble  substances,  as 
sugar,  are  dissolved  in  it.  Starch  is  converted  into  sugar  : 
3(QH,o05)+3H,0=QHiA+2(QH,o05)+2H.O=3(QH,,06) 

Starch  grape  sugar  dextrin  grape  sugar. 

According  to  Mering  the  starch  yields  dextrin  and 
maltose  and  later  grape  sugar. 

515.  Parotid  saliva:  the  following  is  Hoppe-Seyler's 
analysis  of  human  parotid  saliva:        ' 

Water 99.32 

Solids 0.68 

Mucin,    epithelium     and     soluble    organic 

bodies O.34 

Potassium  sulphocyanide O.03 

Inorganic  salts 0.34 

It  is  a  clear  liquid,  not  viscous,  but  slightly  alkaline. 
It  gives  no  reaction  for  mucin,  but  contains  albumin,  pty- 
alin,  and  sulphocyanide  of  potassium. 

Among  more  or  less  peculiar  constituents  we  find  para- 
globulin,  caproic  acid,  urea,  and  traces  of  sulphates.  The 
reaction  of  the  first  secreted  parot'd  saliva  is  less  alkaline 
than  that  secreted  later,  although  according  to  Astach- 
ewsky,  it  has  a  faintly  acid  reaction  that  gives  place  to  an 
alkaline  reaction,  when  the  mucous  membrane  of  the 
mouth  is  slightly  irritated. 

On  standing,  the  parotid  secretion  becomes  turbid, 
owing  to  the  escape  of  carbonic  acid  and  the  consequent 
precipitation  of  calcium  carbonate.  Parotid  saliva  varies 
in  quantity  during  the  day,  less  being  secreted  immed- 
iately after  a  meal.     (Charles). 

516.  Submaxillary  saliya:  in  the  dog,  this  saliva  con- 
tains 99.44  water  and  0.59  solids.  Of  the  latter,  mucin 
and  epithelium  form  0.066  parts,  soluble  organic  bodies 
0.17,  inorganic  salts  0.43.     The  character  of  submaxillary 


354  DENTAL    CHEMISTRY. 

saliva  depends  on  the  exciting  stimulus  to  its  secretion; 
stimulation  of  the  cJiorda  tyinpani  nerve  causes  a  normal, 
rich  alkaline  secretion,  as  noticed  when  acids  are  applied 
to  the  surface  of  the  tongue,  but  in  it  no  pytalin  is  found; 
with  long  continued  stimulation  the  organic  solids  dimin- 
ish somewhat,  though  at  first  the  mucin  is  especially  in- 
creased; stimulation  of  the  sympathetic,  as  on  application 
of  pepper  or  alkalies  to  the  tongue,  produces  a  strongly 
alkaline  secretion,  of  high  specific  gravity,  1.007  ^o  1.018, 
but  viscid,  turbid,  slowly  flowing,  rich  in  mucus  and  ir- 
regularly formed  cell  elements. 

\x\  chordal  saliva  (submaxillary),  Heidenhain  gives  the 
solids  as  3  per  cent.,  2.5  organic  and  0.5  inorganic;  but 
other  authorities  give  1.2  to  1.4  per  cent.  In  syinpatJictic 
saliva  (submaxillary)  Heidenhain  gives  5.8  per  cent, 
solids,  Eckhard  2.7  per  cent.  In  paralysis  of  the  nerves 
supplying  the  gland  very  watery  saliva  is  found,  contain- 
ing little  solids  or  mucus,  hi  general,  it  may  be  said  of 
saliva  that  it  cojitains  a  comparatively  large  quantity  of  mucin 
dissolved  in  an  alkaline  fluid,  together  with  a  sugar-forming 
ferment,  and  potassiu7n  sulphocya?iide.  Submaxillary  saliva 
is  comparatively  poor  in  ptyalin,  while  parotid  is  rich  in 
it;  submaxillary  saliva  is  rich  in  mucin,  while  parotid  is 
poor  in  it.  The  submaxillary  saliva  is  more  alkaline 
than  parotid  and  more  viscid.  Its  average  specific  gravity 
is  from  1.002  to  1.003.  It  contains  much  more  carbonic 
aciu  than  is  found  in  venous  blood,  but  is  poorer  in  nitro- 
gen.     (Pflueger). 

517.  Sublingual  saliTa:  this  saliva  is  very  viscous  and 
thready,  strongly  alkaline,  rich  in  mucus  and  salivary 
corpuscles,  and  would  appear  to  be  the  richest  in  solids 
of  all  salivas.  Heidenhain  found  2.75  per  cent,  of  solids 
in  the  dog.  Traces  of  cholesterin  and  fat  have  been 
found.     (Charles). 

518.  Buccal  mucus:    the  amount  of  this  is  inconsid- 


THE  TEETH  AND  THE  SALIVA,  355 

erable  and  it  contains,  according  to  Bidder  and  Schmidt, 
99  per  cent,  of  water.  Its  reaction  is  said  to  be  acid;  it 
contains  numerous  form  elements,  flattened  epithelial 
cells,  and  salivary  corpuscles.  Claude  Bernard  found 
buccal  mucus  alkaline;  the  acid  reaction  would  appear  to 
be  due  to  alteration. 

519.  Circumstances  favoring  the  diastatic  action  of 
saliva : — 

I.  Quality  of  saliva  (parotid  acting  more  slowly  than 
submaxillary);  quality  of  starch. 

II.  Presence  of  acid  7ip  to  0.005  per  cent. 

III.  Dilute  alkaline  solutions  at  104  F.° 

520.  Circumstances  2>//^;7^r/;/^  2x^///«  or  suspending  ^\2i^- 
tatic  action : 

I.  Strong  alkalies,  acids,  temperatures  above  I58°F, 

II.  Temperature  at  or  near  freezing  point, 

521.  Clianges  in  the  saliva:  the  quantity  is  not  con- 
stant even  normally.  Its  secretions  may  be  excited  by 
the  sight  or  even  thought  of  food,  by  the  movements  of 
mastication,  by  vapors  of  ether  or  acetic  acid,  or  by  elec- 
tric excitation.  If  Jacobson's  nerve  be  stimulated,  a 
watery  secretion  occurs  with  diminished  ptyalin,  albumin, 
and  salts;  if  there  is  stimulation  of  the  sympathetic  at 
the  same  time,  a  copious  secretion  is  obtained,  in  which 
the  organic  constituents  are  in  abundance,  with  a  slight 
increase  of  the  salts. 

Circumstances  which  increase  the  quantity  in 
twenty-four  hours : 

I.  Dry  food  and  tooth-filling. 

II.  Debility;  confluent  small-pox;  at  end  of  typhoid 
fever;  ague. 

III.  Certain  drugs:  mercury,  pilocarpine,  eserine. 

IV.  Dentition. 

V.  Pregnancy. 

VI.  Hysteria;  facial  neuralgia;  idiocy;  hemiplegia 
from  cerebral  cause. 


356  DENTAL   CHEMISTRY. 

VII.  Water-brash;  organic  diseases  of  the  stomach  or 
abdominal  viscera. 

VIII.  Stomatitis;  ulceration  of  buccal  mucous  mem- 
brane. 

IX.  Injury  from  mineral  acids  taken  internally. 
Among  the  drugs  which  have  been  known  to  produce 

salivation  are  bromine,  arsenic,  antimony,  lead,  prussic 
acid,  nux  vomica,  gold,  cantharides,  digitalis,  conium, 
belladonna,  opium,  iodide  of  potassium  particularly,  io- 
dine, copper,  croton  oil,  colchicum.  In  mercurial  ptya- 
lism,^/^r  of  the  breath  and  sponginess  of  the  gums  are 
common,  but  these  characters  have  been  observed  in  sali- 
vation from  arsenic  and  bismuth.  Extremely  minute 
doses  of  mercury  will,  in  some  persons,  rapidly  bring  on 
salivation. 

Certain  substances,  as  bark  of  pyrethrum.  tobacco,  etc., 
excite  the  buccal  mucous  membrane  and  lead  to  saliva- 
tion. 

522.  Circumstances  decreasing  the  quantity  of 
saliva: — 

I.  Fevers  and  inflammatory  diseases. 

II.  Certain  drugs,  particularly  belladonna  and  atro- 
pine. 

523.  Circumstances  rendering  the  saliva  acid  in 
reaction : — 

I.  Decomposition  of  organic  substances  in  the  mouth. 

II.  Diabetes.  (Saliva  acid  when  secreted,  and  some- 
times contains  lactic  acid). 

III.  Catarrh  of  the  mouth  and  intestinal  tract. 

IV.  Acute  rheumatism. 

V.  Mercurial  salivation. 

VI.  Occasionally  in  carcinoma  of  the  liver  and  in  ty- 
phus fever,  in  muguet,  and  frequently  in  dyspepsia, 
though  in  the  last  possibly  due  to  acid  mucus.  Changes 
in  the  reaction  of  the  saliva  due  to  decomposition  of  food 


THE  TEETH  AND  THE  SALIVA.  357 

in  the  mouth  must  be  carefully  distinguished  from  changes 
due  to  disease.  In  the  former  case  the  saliva  may  be  se- 
creted of  alkaline  reaction,  but  in  the  latter  case  it  comes 
acid  from  the  ducts. 

524.  Circumstances  giving  rise  to  odor  in  the 
saliva: — 

I.  Gingivitis. 

II.  Scurvy. 

III.  Mercurial  salivation. 

IV.  Angina. 

A  fetid  odor  has  been  noticed  in  the  above  named  dis- 
eases. 

525.  Circumstances  increasing  the  amount  of  solids 
in  the  saliva  or  producing  abnormal  solid  constituents: 

I.  Mercurial  salivation. 

II.  Bright's  disease,  (urea  abundant). 

III.  Hysteria,  (leucin  found). 

IV.  Phlegmasia. 

526.  Circumstances  decreasing  tlie  amount  of 
solids  :— 

1.     Chlorosis,  (water  increased). 

527.  Tartar:  while  the  secretions  of  the 
mouth  remain  alkahne,  there  is  a  tendency  to 
deposit  Hme  compounds  on  the  teeth.  This 
constitutes  tartar,  and,  although  it  protects  the 
body  of  the  tooth,  it  has  an  injurious  effect  on 
the  gums.  When  the  secretions  of  the  mouth 
become  acid,  tartar  is  no  longer  deposited, 
and  the  decay  of  the  teeth  usually  hastened. 
(Leffman). 

Soft  tartar,  such  as  is  found  at  the  necks,  especially  of 
the  back  teeth  of  youth,  is  destructive,  holding  acids  in 
loco.     (Chandler). 


358  DENTAL   CHEMISTRY. 

Tartar  is  of  grayish,  yellowish,  or  brownish  color;  Icp- 
tothrix  biiccalis  is  found  in  it;  it  consists  chiefly  of  calcium 
phosphate,  with  a  little  calcium  carbonate,  and  phosphate 
of  iron.  According  to  Charles  its  average  composition  is 
as  follows: 

Per  cent. 

Calcium   phosphate 55  to  64 

"  carbonate 7  to     8 

Ferric  phosphate i  to     3 

Residue:  organic  matter,  salts  of  alka- 
lies, silica,  etc 24  to  28 

Magitot  held  that  tartar  in  the  region  of  the  parotid 
was  almost  wholly  carbonate,  other  tartar,  phosphate. 
Alfred  Vergne  on  the  contrary  claims  that  molar  tartar 
has  less  phosphate  than  incisor,  but  that  the  carbonate  is 
about  evenly  divided. 

528.  Salivary  Calculi:  saliva  exposed  to 
the  air  becomes  covered  with  a  fihii  of 
calcium  carbonate.  Concretions  of  this  sub- 
stance are  often  found  in  the  salivary  ducts, 
in  which  case  they  are  known  as  salivary 
calculi.  These  are  of  an  elongated  form,  dirty 
white  color,  and  formed  in  concentric  layers. 
They  vary  in  size,  appearance,  and  composi- 
tion. They  contain  no  leplothrix.  Their 
average  composition  is,  according"  to  Charles,, 
as  follows: 

Per  Cent. 

Calcic  phosphate 30  to  80 

"        carbonate 1 1  to  1 5 

Organic  matter 5  to  25 

Magnesium  oxide,    iron   oxide,    sodium   chloride,  sul- 


THE  TEETH  AND  THE  SALIVA.  359 

phates,   and    potassium    sulphocyanide,   have     all    been 
found  in  salivary  calculi. 

529.  Uric  acid  calculi  have  been  found  in  the  ducts  in 
patients  of  an  uric  acid  diathesis.  Acids  dissolve  the 
ordinary  salivary  calculi  very  rapidly,  considerable  gas 
being  given  off  owing  to  the  abundance  of  calcium 
carbonate  present. 


CHAPTER  VI. 


EXPERIMENTS    ILLUSTRATING   GENERAL    PRINCIPLES    OF 
CHEMISTRY. 

530.    Apparatus  and  Manipulations.— 

Test-  Tubes  ( fig.  1 )  are  conveniently  about 
four  inches  long  and  five-eighths  of  an  inch  in 
diameter.  Longer  and  narrower  ones  are  some- 
times useful.  Test-tubes  are  small,  thin,  glass 
tubes  closed  at  the  rounded  end,  and  slightly 
flared  at  the  mouth. 

Care  is  to  be  taken  not  to  crush  the 

tubes   between    the  fingers,  not  to 

drop  them  on  the  floor  or  into  the 

sinks,  not  to  push  the  brush  (fig.  2) 

through  them  when   cleaning,   and 

not  to  crack  or  break  thembyhold- 

them   steadily   in  a  hot  flame,  not 

even  when  full  of  liquid,  nor  to  let  any  flame  touch  any 

part  of  them,  unless  they  are  filled  with  liquid.     Care 

should   also   be  taken  not  to  pour  any  liquid  into  them 

3()0  ^ 


Fig.  I. 


EXPERIMENTAL    CHEMISTRY. 


361 


BmaoA 


when  they  are  broken,  especially  at  the  bottom.  They  should 
always  be  set  in  their  place  in  the  rack,  when  filled  with 
liquid,  and,  when  empty,  should  be  inverted,  after  clean- 
ing, over  the  pegs.  The  good  student  in  chemistry  may 
be  recognized  by  the  good  condition  of  his  test-tubes  and  racks. 

Funnels    (fig.     3)     used     are    of 
glass;  those   three   or   four   inches 
F^s-  2.  in  diameter   across   the  top  are  of 

convenient  size. 

Filter  paper  \s  unsized  paper;  the  best  is  called  Swedish, 
and  may  be  bought  already  cut  in  circular  form.  Filter 
papers,  seven  and  a  half  inches  in  diameter,  fit  well  into 
the  funnels  above  described.  In  order  to  fold  a  filter  so 
as  to  fit  it  into  the  funnel,  first  fold  it  in  two,  then 
turn  the  right  half  over  the  left.  In 
this  way  a  funnel  shape  is  given  to  the 
paper.  Fit  it  into  the  funnel,  and  the 
edges  should  not  project  over  the  rim 
of  the  latter.  Set  the  funnel  into  a 
test-tube  with  a  slip  of  paper  between 
the  funnel  and  the  tube,  so  as  to  allow 
free  passage  of  air.  The  test-tube  must, 
of  course,  stand  in  the  rack.  If  large 
quantities  of  a  liquid  are  to  be  filtered, 
the  funnel  should  be  set  in  a  ring  on 
the  ring  stand  (fig.  3)  or  supported  by 
a  clamp  with  a  beaker  under  it,  the 
lower  end  of  the  funnel  touching  the 
beaker  so  that  the  liquid  runs  dpwn  its 
side   gently.      The  liquid   which    runs  ^'^z-z- 

through  the  filter  is  called  \he  filtrate,  and,  as  a  rule,  the 
filter-paper  should  be  wet  with  water  and  the  water 
allowed  to  run  through,  before  adding  the  liquid  to  be 
filtered. 


362 


DENTAL    CHEMISTRY. 


A  beaker  (fig.  4)  is  a  thin,  glass  vessel  with  a  flat  bottom. 
Those  holding  100  c.c.  to  150  c.c.  are  convenient  to  use, 
and  watch  glasses  serve  well  as  covers.  Beakers  are  com- 
monly sold  in  nests,  as  in  the  figure, 
A  burette  (fig.  5)  is  a  long,  nar- 
row tube,  provided  with  a  stop- 
cock, or  pinch-cock,  to  control  flow 
of  liquid  from  it.  Burettes 
are  to  be  had  graduated  in 
the  metric  system  in  cubic 
centimeters,  provided  with 
glass  stop-cocks,  and  are, 
when  used,  held  by  what  is 
known  as  the  burette  holder 
or  support  (fig.  6). 
K pipette  (fig.  7)  is  the  name  given  to  the  simp- 
lest form  of  burette,  which  is  merely  a  glass  tube 
filled  by  suction,  and  the  liquid  returned  by  pressure 
of  the  finger  on  the  top  of  the  tube,  the  flow  of  liquid 
being  controlled  by  the  finger. 

The  washing-bottle  (fig.  8)  consists  of  an  ordinary 
bottle  or  flask,  provided  with  a  doubly  perforated 
stopper  through  which  pass  two  pieces  of  glass  tub- 
ing. Blowing  into  the  shorter  tube  throws  the  water 
out  in  a  stream  from  the  longer  one. 

Glass-tubing  may  be  bent  by  using  the  flaring  flame, 
obtained  by  means  of  the  wing-top  of  the  Bunsen 
burner.  After  the  glass  softens  in  the  flame  it  should  ^>k-5- 
be  removed  from  it,  and*  gently  bent  into  any  shape  re- 
quired. While  heating  the  glass,  rotate  it  slowly  in  the 
flame.  Glass  tubes  are  drawn  out  by  heating  in  the  non- 
luminous  Bunsen  flame. 

Glass  rods  may  be  cut  by  use  of  a  triangular  file.     Make 


m. 


EXPERIMENTAL    CHEMISTRY. 


363 


one  sharp,  deep  scratch  and  break  off  with  the  thumb 
and  fingers  of  each  hand,  placed  on  each  side  of  the  scratch. 
Irofi  rifig  statids  (fig.  3),  or  supports,  consist  of  an  iron 
rod,  inserted  into  a  base  of  the  same  material,  and  pro- 
vided with  rings,  which 
slide  up  and  down  the  rod, 
being  fastened  by  means 
of  a  screw  at  any  desired 
height.  Into  the  rings 
may  be  set  funnels  or  beak- 
ers, the  latter  protected 
from  the  naked  flame  be- 
low, when  used,  by  inter- 
position of  a  sand-bath, 
wire  gauze,  or  asbestos 
sheet. 

The  sand-bath  is  merely 
a  shallow  iron  dish  filled 
with  sand. 
The    mortar   with   pestle    ^'^•7- 
(fig.  9)  is  used  for  pulverizing  substances,  and  the  spatula 
(fig.  10)    is   useful   for   removing 
powder  which  sticks  to  the  mortar. 
The  Bunsen  burner  (figs.  11    to 
19)  is  an  important  piece  of  ap- 
paratus.    Figs.  11-19  show  differ- 
ent kinds,  of  which  fig.  14  is  the 
ordinary.     It  is  attached  to  a  gas 
jet   by   means    of   rubber   tubing. 
The  openings  at  the  lower  part  of 
the  Bunsen  tube  allow  air  to  enter, 
and  cause  more  perfect  combus- 
tion of  the  gas,  which  results  in 
the  production  of  a  non-luminous, 


Fig.  6. 


Fig.  8. 


364 


DENTAL    CHEMISTRY. 


Fig.  9. 


Fig.  II. 


Fig.  12. 


Fig.  15. 


Fig.  13. 


Fig.  14. 


Fig.  16. 


EXPERIMENTAL    CHEMISTRY. 


365 


smokeless  flame.  In  order  to  light  the  Bunsen  burner 
turn  on  the  gas  from  the  gas  jet,  light  a  match,  and,  with 
an  upward  movement  of  the  hand,  raise  the  lighted  match 
quickly  up  past  the  tip  of  the  Bunsen.  Do  not  light  the 
burner  by  slowly  lotvering  the  lighted  snatch  from  above 
downward. 


Fig.  17. 


In  case  the  flame,  without  change  in  the  collar,  sud- 
denly becomes  luminous,  after  being  non-luminous,  "run- 
ning back"  has  taken  place,  and  it  will  be  seen  that  the 
gas  is  also  burning  below.  Turn  out  the  gas  and  light  over 
again  as  above,  taking  the  precaution  also  to  close  the 
revolving  collar  partially. 


Fig.  20. 


Fig.  21. 


Fig.  22. 


The  wire  triangle,  (fig  20),  one  corner  of  which  is  thrust 
through  a  cork,  is  useful  for  observing  the  action  of  heat 
on  substances,  the  cork  being  held  in  the  hand  while 
heating  the  substance  on  the  triangle. 

The  cork-borer  (fig.  21)  consists  of  metal  tubes  with  cut- 


366 


DENTAL    CHEMISTRY. 


Fig.  23. 


ting  edgec  perforated  at  one  end.  Through  the  perfora- 
tion a  small  rod  of  metal  being  thrust  a  handle  is  thus 
made.  After  the  cork  has  been  bored,  a  fragment  of  it 
remains  in  the  metallic  tube.  Remove  now  the  rod  and 
push  the  piece  of  cork  out  of  the  tube  with  it. 

Corks  may  also  be  bored  by  piercing 
with  a  small  round  file,  and  filing  the 
aperture  made  to  any  desired  size. 

The  spirit-lamp  (fig.  22)  is  useful  when 
but   slight  heat  is   needed.       Put   the 
flame  out,  when  necessary,  by  covering  with  the  cap. 

The  porcelain  dish  (fig.  23)  is  useful  for  evaporating  pur- 
poses. As  long  as  there  is  liquid  in  the  dish,  it  may 
simply  rest  in  the  ring  in  the  iron  ring-stand,  but  if  the 
evaporation  is  to  be  carried  to  dry- 
ness, use  the  water-bath.  The  latter 
(fig.  24)  is  usually  made  of  copper, 
and  is  a  roundish  vessel,  provided 
with  a  series  of  concentric  rings.  The 
size  of  the  evaporating  dish,  to  be 
placed  on  the  water-bath,  regulates 
the  number  of  rings  to  be  used  as  support  for  the  dish. 
Plati?ium  wire  is  useful  for  heating,  or  fusing  substances 
in  the  Bunsen  flame.  The  wire  is  moistened  and  dipped 
into  a  powder,  which  adhering  to  the  wire  may  be  fused 

in  the  flame,  and  the  color  im- 
parted by  it  to  the  colorless 
flame  thus  noticed. 

Platifium  foil  is  of  use  in  ob- 
^'&-  25-  serving  the   action   of  heat  on 

substances,  as  is  also  \hQ  platifmm  dish.  A  platinum  dish, 
(fig.  25)  which  holds  about  15  c.c.  or  half  a  fluid  ounce, 
weighs  about  10  grammes  and  costs  about  $5.00.  Plati- 
num materials  withstand  the  Bunsen  flame  and  al:;o  the 


Fig.  24. 


EXPERIMENTAL   CHEMISTRY. 


3C7 


mineral  acids,  except  aqua  regia,  hence  can  be  kept  clean 
by  use  of  acid,  as  hydrochloric.  They  may  be  bright- 
ened by  polishing  with  fine,  white  sea  sand. 

Litmus  and  turmeric  papers  are  used  to  distinguish  acids 
from  alkalies.  Litmus  paper  is  of  two  colors,  blue  and 
red.     Blue  litmus  is  turned  red  by  acid  solutions,  and  red 


Fig.  26. 


Fig.  27. 


libmus  turned  blue  by  alkaline  solutions.  Litmus  paper 
in  quantity  must  be  wrapped  up  carefully,  and  kept  away 
from  light  and  air.  For  use  in  the  laboratory  small,  nar- 
row slips  of  it,  kept  in  a  wide-mouthed  bottle  tightly 
corked  and  covered  over  with  paper,  are  convenient. 
Turmeric  paper  is  yellow  and  is  turned  brown  by  alkalies. 


368 


DENTAL    CHEMISTRY. 


Acids  do  not  affect  it.    '  It  is  used  chiefly  for  detection 
of  borax  (see  Qualitative  Analysis). 

Glass  stoppered  reagent  bottles  (figs.  26  and  27)  which  are 
now  used  in  laboratories  have  the  chemical  names  and 
formulae  in  raised  letters,  ground  in  the  surface.  When 
of  a  capacity  of  four  ounces  they  cost  about  §1.75  a 
dozen,  eight  ounces  $2.50  a  dozen. 

The  following  is  a  list  of  those  commonly  used: 


Inorganic. 


Formula. 


HCl 


HNO3 

H,S 

H4NHO 

or 
NH4HO 

or 
AmHO 

(NHJ.MoO, 
NH4CI 

(NH,)3C03 
(NH,),S 

NH4HS 
NaHO  or  OH 


Label. 


Hydric  chloride 


Hydric  sulphate 


Hydric  nitrate 
Hydric  sulphide 


Ammonic  hydrate 
or  hydroxide 


Ammonic  molybdate 
Ammonic  chloride 

Ammonic  carbonate 
Ammonic  sulphide 
Ammonic  hydro-sulph- 
ide or  sulphydrate 
Sodic  hydrate  or 
hydroxide 


Commercial  Name. 


(  Hydrochloric 
\  acid  at  muri- 
I    atic  acid 

!Su 1 ph  ur  i  c 
acid  or  oil 
of  vitriol 

j  Nitric  acid  o'*' 
I    aqua    fort  is 

\  Sulphuretted 
I    hydrogen 

"Ammonia." 
(Aqua) 


Sal  ammoniac. 
Sal  volatile. 


Caustic  Soda. 


EXPERIMENTAL    CHEMISTRY. 

Inorganic — Continued. 


369 


Formula. 


Na^HPO^ 


Na^COj 


K,C03 


KI 

KHO 
K,CrO, 

Agx\03 
BaCl^ 

BaCOg 

Ba(HO), 

or 
BaOH.^O 

CaCl., 

Ca(HO), 
or 

CaSO^ 


Label. 


Di-sodic  hydric  phos- 
phate 

Sodic  carbonate 
Potassic  carbonate 

Potassic  iodide 

Potassic  hydrate  or 
hydroxide 

Potassic  chromate 

Potassic  acid  chromate 
or  dichromate 

Argentic  nitrate 
Baric  chloride 

Baric  carbonate 

Baric  hydrate 

Calcic  chloride 
Calcic  hydrate 

Calcic  sulphate 


Commercial  Name. 

Phosphate  of 
sodium. 

(  Carbonate   of 
I    sodium. 

(  Carbonate   of 
I    potassium. 

j  Iodide  of  po- 
(    tassium. 

Caustic  potash, 
potassa. 

j  Chromate   o  f 
I    potash. 

Bichromate  of 
potash. 

Nitrate  of  silver 

(  Chloride   o  f 
I    barium. 

(  Carbonate  o  f 
(    barium. 

Caustic  baryta. 

(Chloride  of 
(    calcium. 

(Slaked  lime, 
lime  water, 
etc.). 

Sulphateof  cal- 
cium or  sulph- 
ate of  lime. 


370 


DENTAL   CHEMISTRY. 


Inorganic. — Continued. 


Formula. 

Label. 

Commercial  Name. 

"^Sulphate  o  f 

magne  s  i  u  m 

MgSO, 

Magnesic  sulphate 

or  sulphate 
of   magnesia 
or    "Epsom 
^  salts." 

CuSO^ 

Cupric  sulphate 

Blue  vitriol. 

HgCl, 

Mercuric  chloride 

j  Corrosive 
(    sublimate. 
(  Green   vitriol 

FeSO^ 

Ferrous  sulphate 

or 
(  copperas. 

Fe,Cl« 

Ferric  chloride 

j  Fere  h  1  o  r  i  d  e 
(    of  iron. 

PtCl, 

Platinic  chloride 

Organic. 


Formula. 

Label. 

Commercial  Name. 

K^FeCy, 

Potassic  ferrocyanide 

(  Yellow  prus- 
<  siate  of  pot- 
(    ash 

KaFeCy, 

Potassic  ferricyanide 

(  Red  prussiate 
1    of  potash. 

KCyS 

(NH,),C,0,-] 

or 

Potassic  sulphocyanide 

(H,N),C,0,  I 

Ammonic  oxalate 

Am,C,0,  j 
Pb(C,H  O,)., 

Plumbic  acetate 

Sugar  of  lead. 

QH,„o 

Ether 

Sulphuric  ether 

EXPERIMENTAL    CHEMISTRY. 

Organic — Continued. 


371 


Formula. 


C,H,0    - 

or 
C^H.HO 

or 
C,H,OH    , 

H(CoH302) 


Label. 


Alcohol 


Hydric  acetate 


Commercial  Name. 


Acetic  acid. 


The  bottles  in  question  are  either  wide-mouthed  and 
provided  with  mushroom  stoppers  (preferably  in  the  case 
of  solids)  or  with  flat  stoppers  usually  in  the  case  of 
liquids.  Mushroom  stoppers  when  removed  may  be 
placed  upside  down  on  desk,  but  flat  stoppers  should 
be  held  between  the  second  and  third  finsfer  of  the  hand 


Fig.  28. 


Fig.  29. 


in  which  the  bottle  is  taken,  except  in  case  of  acids. 
When  the  bottle  contains  an  acid,  hold  the  flat  stopper 
upright  in  the  hand  which  holds  the  test-tube. 

Liquids  may  be  poured  out  of  these  bottles,  drop  by 
drop,  by  loosening  the  stopper  slightly  and  then  prevent- 
ing the  stopper  from  falling  out  by  use  of  the  fore-finger. 


372 


DENTAL    CHEMISTRY. 


Solids  may  be  poured  from  the  wide-mouthed  bottles  by 
gently  rotating  in  a  horizontal  position. 

The  blow-pipe  attd  its  uses  are  described  in  full  in  the 
chapter  on  Analytical  Chemistry. 

TYiQ  chemical  balance  for  ordinary  weighing,  in  experi- 
mental work  need  not  be  expensive.  An  ordinary  hand- 
balance  serves  most  purposes  but  a  more  exact  form  of  bal- 
ance is  shown  in  figures  28  and  29.  Such  balances  are  to  be 


.^ 


-Qr- 


-Or 


^ 


Ch 


-^^ 


^^ 


Fig.  30. 


had  all  brass  with  steel  bearings,  movable  pans,  and  sensitive 
to  -^Q  grain.  Metric  weights  will,  however,  be  needed  for 
the  experiments  herein  described.  For  most  purposes 
the  set  of  metric  weights  from  20  grams  down  to  i  centi- 
gram is  sufficient.  Weights  should  be  handled  always 
with  the  forceps,  and,  to  prevent  corrosion  of  the  pans, 
slips  of  glazed  paper  of  equal  weight  may  be  used  in  each 
It  is  often  necessary  to  weigh  the  various  vessels  used  in 


EXPERIMENTAL    CHEMISTRY. 


373 


an  experiment;  for  that  purpose  counterpoising  is  more 
convenient.  Counterpoise  the  empty  vessel  with  fine  dry 
sand,  fill  the  vessel  as  required  and  weigh.  The  weights 
used  represent  the  weight  of  the  contents  of  the  vessel. 

Figure  30  represents  a  chemical  balance  of  improved 
type,  for  accurate  quantitative  work. 

Graduates  (fig.  31)  for  measuring 
liquids  are  very  convenient  to  have  on 
hand,  and  should  be  of  several  sizes. 
The  metric  unit  of  liquid  measurement 
is  the  cubic  centimeter,  abbreviated  to 
c.  c.  or  cc,  which  represents  distilled 
water  of  sufficient  volume  to  weigh 
one  gramme  or  15.43  grains  Troy,  at 
15°  Centigrade,  (60°  Fahr- 
enheit). The  most  convenient 
graduates  are  those  with  the 
double  graduation  in  c.  c.  and 
fluid  ounces,  up  to  1,000  c.  c, 
32  fluid  ounces.  Minim  grad- 
uates (fig.  32)  occasionally  come  in  handy,  and  also  those 
holding,  say,  40  c.  c,  and  200  c.  c.  Remember  that  30  c.  c. 
equals  about  one  fluid  ounce.  Special  apparatus  such  as 
gas  generators,  endiometers,  and  U-tubes  will  be  described 
under  the  particular  heading  where  they  are  mentioned. 
Yarioiis  Manipulations:— In  dealing  with  liquids  the 
following  manipulations  are  common: — 

1.  Boiling: — Liquids  may  be  boiled  in  test-tubes  ovei 
the  Bunsen  flame,  when  but  small  quantity  is  to  be  used 
and  the  boiling  not  to  be  prolonged.  Cut  out  a  strip  of 
paper  and  wrap  it  round  a  test-tube,  holding  by  the  pro- 
jecting ends,  during  the  process  of  boiling.  Point  the 
tube  away  from  every  person  near-by,  including  yourself, 
so  that  if  sudden  or  violent  boiling  takes  place,  no  one 


Fig.  32. 


FiK.  31. 


374 


DENTAL    CHEMISTRY. 


may  suffer  from  it  Do  not  remove  the  hot  liquid  quickly 
from  the  flame,  and  then  look  down  into  the  tube,  lest  it 
suddenly  boil  up  into  the  face.  To  prevent  too  vigorous 
boiling  rest  the  lower  end  of  the  test-tube  on  the  rim  of 
the  tube  of  the  Bunsen  burner,  remembering  that  the 
hottest  part  of  the  Bunsen  flame  is   the  top  of  the  inner 


Fig.  33- 


Fig.  34-  Fig.  33. 

cone  of  flame.  What  is  known  as  a  clamp  (fig.  33)  is  use- 
ful for  holding  the  test-tube;  for  prolonged  boiling  use  a 
cla?np-stand  or  stipport  (fig.  34). 

To  boil  larger  quantities  of  liquids,  above  15  c.c.  (half 
an  ounce),  beakers  are  to  be  used;  resting  as  stated  before 
on  asbestos  sheets  or  gauze,  and  placed  on  the  rings  of 
the  ring  stands  (fig.  35). 

2.  Pouring: — To  pour  liquids  from  one  vessel  to 
another  hold  a  glass  rod  or  tube  vertically  close  to  the 


EXPERIMENTAL  CHEMISTRY.  375 

lip  of  the  containing  vessel,  and  the  liquid  will  follow  the 
rod  rather  than  spill. 

In  pouring  large  quantities  of  liquid  from  one  vessel  to 
another  see  that  the  liquid  strikes  the  side  of  the  vessel 
into  which  it  is  poured,  rather  than  the  bottom.  In  this 
way  splashing  is  avoided.  Great  care  is  thus  to  be  taken 
in  pouring  acids  and  strong  ammonia  water  from  one 
vessel  to  another. 

In  mixing  sulphuric  acid  and  water  the  acid  must  be 
poured  in  small  quantities  only  into  the  water,  and  not 
water  into  the  acid,  since  great  heat  is  evolved,  and  the 
mixture  may  boil  with  explosive  violence. 

In  mixing  acids  with  strong  alkalies  or  dissolving  the 
latter  in  water,  heat  is  generated.  Take  care  that  the 
containing  vessel  does  not  crack  during  the  process,  and 
that  the  hands  are  not  burned  or  the  clothing  injured. 

Opening  bottles: — 

In  opening  bottles  whose  stoppers  resist  the  strength 
of  the  fingers,  first  tap  the  stopper  near  its  neck  with 
anything  convenient;  as  a  glass  rod,  and  then  twist;  if 
now  ft  does  not  come  out,  put  the  neck  of  the  bottle  into 
hot  water  for  a  short  time  and  try  tapping  again. 
If  this  is  not  successful,  gently  heat  the  neck  of  the  bot- 
tle over  the  alcohol  flame,  rotating  with  great  care.  If 
this  fails  to  loosen  the  stopper,  take  a  sharp  file  and  file 
thoroughly  about  the  neck,  then  hit  the  head  of  the  bot- 
tle a  sharp  rap  with  a  comparatively  heavy  substance, 
as  a  small  hammer  or  pestle  end,  and  the  neck  and  stopper 
will  be  knocked  off  without  damage  to  the  body  of  the 
bottle. 

Bottles  containing  sodic  hydrate  should  have  their  glass 
stoppers  paraffined,  which  is  done  by  simply  dipping 
the  lower  part  of  the  stopper  into  melted  parafiine.  This 
prevents  adhesion  of  the  stopper  to  the  neck  of  the  bottle. 


376 


DENTAL    CHEMISTRY. 


List  of  Apparatus  Required.* 

The  apparatus  required  to  perform  the  experiments 
next  to  be  described  is  as  follows: — 

1.  Test-tube  racks,  each  with  a  dozen  test-tubes,  which 
are  four  inches  long  by  five-eighths  of  an  inch  in  diameter 

2.  Test-tube  brushes,  two  for  each  student. 

3.  Glass  funnels,  one  or  two  for  each  rack. 

4.  Filter  papers,  cut  in  packages  of  100  each. 

5.  Beakers,  one  or  two  for  each  student  with  watch 
glasses  for  covers. 

6.  Hard  glass  tubes,  small  with  closed  ends  (ignition 
tubes),  say  two  and  one-half  inches  long;  several  for 
each  student. 

7.  Wash-botties,  one  for  each  rack. 

8.  Glass  rods,  two  for  each  student. 

9.  Glass  tubing,  ad  lib. 

10.  Pipettes,  one  or  two  for  each  stu- 
dent, 

11.  Burettes,  one  or  two  for  each  student. 

12.  Graduated  burettes,  one  for  every  three  or  four 
students. 

13.  Iron  ring  stands,  or  tripods,  one  for  every  three  or 
four  students  with  sand  bath,  or  asbestos  sheets,  or  wire 
gauze. 

14.  Mortar  and  pestle. 

15.  Bunsen  burners,  one  for  each  student,  with  rubber- 
tubing  and  wing-top. 

16.  Crucible  tongs  (fig.  36),  and  wire  triangles. 

17.  Shears,  pincers,  files,  knives. 

18.  Cork-borers,  spatulas. 

19.  Alcohol  lamps. 

20.  Porcelain  evaporating  dishes. 


♦To  be  had  of  fdealers  in  chemical  apparatus  as  E.  H.  Sargent,  Chicago. 


EXPERIMENTAL    CHEMISTRY.  377 

21.  Platinum  foil,  wire,  and  dish6s  in  quantity  accord- 
ing to  means. 

22.  Water-baths,  in  convenient  number,  according  to 
means. 

23.  Litmus  and  turmeric  paper. 

24.  Sponges. 

25.  Bottles  of  various  kinds;  a  set  of  glass-stoppered 
reagent  bottles  for  each  student  or  pair  of  students;  a 
couple  of  wide-mouthed  bottles  for  each  student,  provided 
with  cork  or  rubber  stoppers,  one  perforated,  the  other 
not. 

26.  A  blow-pipe  and  charcoal  for  each  student,  or  pair 
of  students. 

27.  A  chemical  balance  with  metric  weights  of  precision. 

28.  Graduates,  for  measuring  liquids,  of  i.ooo  c.c. 
capacity. 

29.  A  good-sized  blackboard. 

30.  Aprons,  rubber  gloves,  protection  glasses,  soap,  and 
towels. 

For  the  benefit  of  those  who  are  inexperienced  it  may 
be  said  that  the  more  expensive  articles  in  the  above  list  are 
the  graduated  burettes  with  glass  stop-cocks,  the  porce- 
lain evaporating  dishes  (according  to  size),  all  platinum 
materials,  water  baths,  the  glass-stoppered  reagent  bot- 
tles, the  1,000  c.c.  graduates,  and  the  chemical  balance. 

Everyone  working  in  a  chemical  laboratory  should  pro- 
vide himself  with  an  apron.  Stains  from  chemicals  are 
usually  seen  on  the  coat-sleeves,  and  on  the  trousers  just 
above  the  knee,  so  that  these  parts  should  be  protected. 
Loose,  flapping  coats  should  not  be  worn,  but  close  fitting 
buttoned-up  sack  coats  are  most  suitable.  Overcoats  and 
hats  should  never  be  brought  into  the  laboratory  as  they 
are  likely  to  be  ruined.  Each  student  should  have  his 
towel,  soap,  and  apron  in  the  drawer  at  his  desk.     Desks 


378  DENTAL    CHEMISTRY. 

should  be  wiped  clean  with  the  sponges  at  the  close  of 
each  exercise.  Instructors  should  consider  the  condition 
of  the  student's  desk  and  outfit  in  grading  him  for  his 
years'  work. 

Special  care  should  be  taken  of  the  eyes.  The  strong 
acids  hydrochloric,  nitric,  sulphuric,  glacial  acetic,  hydro- 
fluoric, the  caustic  alkalies  (ammonia,  caustic  soda  solu- 
tions, caustic  potash  solutions)  bromine,  and  oil  of  must- 
ard are  perhaps  the  most  dangerous  agents,  considered 
with  reference  to  the  eyes.  In  removing  the  stopper  from 
a  large  bottle  of  the  acids,  ammonia  water,  or  bromine 
there  is  quite  frequently  a  puff  of  vapor  which  may  be 
dangerous,  if  received  directly  into  the  eyes.  Even  the 
dilute  ammonia  water  of  pharmacy,  used  for  inhalations, 
has  been  known  to  cause  blindness  through  accidental 
contact  with  the  eyes.  Protection  glasses  should  be  worn 
by  those  handling  large  quantities  of  these'  substances. 

Explosive  mixtures  will  not,  as  a  rule,  be  made  in  the 
course  of  the  work  outlined  here,  but  a  word  or  two  of 
comment  may  not  be  amiss.  Chemicals  which,  either  direc- 
tly or  indirectly,  may  give  rise  to  explosions  are  most  com- 
monly the  following: — 

Potassium  chlorate. 

The  hypophosphites. 

Potassium  permanganate. 

Certain  iodides  and  iodoform, 

Nitric  acid. 

Chromic  acid. 

Bromine. 
Potassium  chlorate  must  not  be  rubbed  up  or  triturated 
with  organic  substances  as,  for  example,  tannin  or  saccharin 
nor  with  certain  sulphides,  as  antimo7iy  sulphide^  nor  with 
the  hypophosphites,  iiitrates,  or  salts  of  iron. 


EXPERIMENTAL    CHEMISTRY.  379 

The hypophosphites  explode  when  triturated  with  chlorate 
of  potassium  and  when  heated. 

Potassiion  perma7iga7iate  is  very  easily  decomposed,  and 
explodes  when  rubbed  up  with  glycerin  and  alcohol. 

lodijte  associated  with  a  liquid  containing  large  quan- 
tities of  ammo?iia  will  give  rise  to  formation  of  iodide  of 
nitrogen,  a  highly  explosive  compound.  (An  organic  com- 
pound of  iodine  called  iodoform  explodes,  when  combined 
with  glycerin  and  silver  nitrate.)  Moreover  iodine  mixed 
with  certain  volatile  oils,  as  spifit  of  turpentine,  gives  rise 
to  explosion. 

Chromic  acid  forms  an  explosive  mixture  with  glycerin. 

Bromi?ie  gives  use  to  explosive  compounds  when  com- 
bined with  either  alcohol  or  oil. 

Nitric  acidshonXd  not  be  mixed  with  organic  compounds, 
as  glycerin,  or  carbolic  acid,  and  all  substances  having 
strongly  acid  reaction  should  not  be  mixed  incautiously 
with  glycerin,  particularly  if  the  acidity  is  due  to  presence 
of  nitric  acid. 

Hydrogen  gas  mixed  with  air  is  explosive  (exercise  25). 
If  water  is  poured  into  sulphuric  acid  the  mixture  boils 
violently. 

In  using  sulphuric  acid  in  gas  generators,  as  for  ex- 
ample in  generating  sulphuretted  hydrogen,  take  care  lest 
through  violent  action  in  the  flask,  the  acid  liquid  is  not 
spurted t^pzvard  through  the  thistle  tube. 

Sodium  hydrate  (caustic  soda)  when  dissolved  in  water 
gives  rise  \.o  great  heat. 

Acids  poured  in  excess  on  alkalies,  their  carbonates  or 
sulphides  cdiuse.  great  effervescence. 

Inflammable  substances  are  alcohol,  ether,  gasolitie,  kero- 
sene.     Metallic  potassium  burns  in   water   and    must  be 


380  DENTAL    CHEMISTRY. 

kept  in  oil.  Phosphorus  is  a  highly  inflammable  substance 
and  students  have  been  dreadfully  burned  by  it.  It  must 
be  kept  under  water. 

Poisofious  or  toxic  substances  used  in  the  laboratory  are 
numerous.  Those  most  dangerous  are  arsenic,  potassic  cya- 
nide, corrosive  sublimate,  carbolic  acid,  morphine,  and  strych- 
nine. Ordinary  illuminating  gas  is  a  dangerous  poison  to 
inhale;  students  are  in  danger  from  it  at  night,  during  sleep, 
when  the  gas  has  been  blown  ouc  by  some  ignorant  person, 
or  when  the  gas  fixtures  leak.  Arseniuretted  hydrogen 
generated  in  the  Marsh  test  for  arsenic  is  a  dangerous 
poison  to  inhale.     (See  Marsh  test). 

The  concentrated  mineral  acids  burn  the  skin  terribly. 
If  an  accident  of  this  kind  happens,  wash  thoroughly  with 
a  large  volume  of  water,  then  apply  solution  of  bicarbon- 
ate of  sodium,  and  subsequently  oil.  Every  student  shoul:' 
know  where  a  solution  of  bicarbonate  of  sodium  is  to  be 
had  in  the  laboratory. 

Experiments  Illustrating  General  Principles 
OF  Chemistry. 

Exercise  1.    Solution. 

A.  Take  up  a  little  potassium  nitrate  on  the 
point  of  a  pen  knife,  and  drop  it  into  half  a  test- 
tube  full  of  distilled  water.  Shake  to  and  fro. 
The  salt  slowly  disappears.  The  action  is  known 
as  solution;  potossium  nitrate  is  said  to  \)q solu- 
ble in  water,  and  to  form  a  colorless  solution. 
Now  add  a  little  more  of  the' salt,  shaking  as  be- 
fore, and  then  a  little  more,  and  soon.  After  a 
certain  amount  has  been  added,  it  will  not  com- 
pletely dissolve,  not  even  if  the  tube  be  shaken 


EXPERIMENTAL    CHEMISTRY.  381 

long  and  vigorously.  In  other  words  the  water 
has  dissolved  all  the  salt  it  can,  and  the  solution 
is  then  said  to  be  saturated.  Now  boil  the 
liquid  and  keep  up  the  boiling  some  little  time; 
the  undissolved  salt  is  finally  dissolved,  hence 
ffotassic  nitrate  is  more  soluble  in  hot  than  in 
cold  water,  a  property  common  to  many  sub- 
stances. Let  the  solution  cool,  and  note  that,  as 
the  tube  grows  cold,  the  salt  is  less  soluble  and 
finally  separates  in  the  form  of  glistening  crys- 
tals. Finally  when  the  solution  is  cold,  pour  off 
the  liquid  into  an  evaporating  dish,  and  evapor- 
ate to  dryness  over  the  water-bath.  A  whitish 
substance  is  obtained,  thus  showing  that  the 
salt  is  still  dissolved  in  the  water,  even  after 
cooling  and  separation  of  a  part  of  the  salt.  The 
residue  obtained  is  called  residue  after  evapora- 
tion. Test  the  solubility  of  potassic  iodide,  and 
magnesic  sulphate. 

B.  SolutioTis  of  reagents: — 

It  is  customary,  for  sake  of  convenience,  to  use  chemi- 
cal substances  in  form  of  solution  for  experiments  and 
tests.  These  solutions  are  known  as  reagents^  and  are  to 
be  made  with  cold  distilled  water.  Make  solutions  of 
the  following  substances  and  keep  them  in  the  reagent 
bottles,  being  careful  to  make  no  mistake  in  regard  to 
the  contents  of  each  bottle: — ten  per  cent,  solutions  of 
ammonic  chloride;  of  sodic  hydroxide,  carbonate,  phos- 
phate, and  acetate;  potassic  chromate,  and  dichromate. 
To  make  a  ten  per  cent,  solution  weigh  out  lO  grammes 
of  the  solid  substance  and  dissolve  it  in  90  cubic  centi- 


382  DENTAL    CHEMISTRY. 

meters  of  distilled  water  (155  grains  in  about  three  fluid 
ounces  of  water).  If  the  reagent  bottles  are  the  eight- 
ounce  size,  dissolve  20  grammes  of  the  substance  in  180 
cubic  centimeters  of  water  (310  grains  in  about  six  ounces 
of  water).  Prepare  also  ten  per  cent,  solutions  of  mag- 
nesia sulphate,  baric  chloride,  and  calcic  chloride. 

Prepare  five  per  cent,  solutions  (5  grammes  of  solid  to 
95  c.  c.  of  water)  of  ammonic  oxalate,  potassic  iodide, 
ferrocyanide,  ferricyanide,  and  sulphocyanide;  also  of 
ferric  chloride,  plumbic  acetate,  argentic  nitrate,  mercuric 
chloride,  and  piatinic  chloride. 

Other  reagents  required  need  special  description,  and 
will  be  referred  to  in  the  chapter  on  Analytical  Chem- 
istry. 

Notice  that  not  all  the  solutions  are  colorless:  potassic 
chromate,  for  example,  is  yellow,  the  dichromate  reddish- 
yellow,  the  ferrocyanide  greenish-yellow.  After  a  little 
practice  the  eye  becomes  so  accustomed  to  the  colors  of 
the  solutions  that  a  desired  reagent  can  be  found  quickly, 
and  time  thus  saved  in  work.  Effort,  should,  therefore, 
be  made  to  identify  the  various  reagents  by  help  of  the 
color  of  the  solutions,  as  feoon  as  possible,  but  care  is  to 
be  used  not  to  confuse  solutions  of  similar  color. 

N.  B.  To  determine  whether  a  substance  is  soluble  in 
water:  digest  it  with  distilled  water,  filter,  and  evaporate 
filtrate  to  dryness  in  porcelain  dish  over  the  water  bath. 
If  anything  has  been  dissolved,  a  residue  will  be  left  in 
tHe  dish. 

Exercise  2.  Inorganic  substances  insol- 
uble in  water: — 

A.  Take  up  a  very  little  black  oxide  of  man- 
ganese on  the  point  of  a  pen-knife,  pour  it  into 
half  a  test-tube  full  of  water,  and  shake  as  before. 


EXPERIMENTAL    CHEMISTRY.  383 

It  does  not  dissolve.  Boil  the  water,  and  still  it 
is  not  dissolved.  The  black  oxide  of  manganese 
is  then  said  to  be  insoluble  in  water. 

This  is  true  also  of  a  large  number  of  other  oxides  of 
the  elements,  but  the  oxides  of  potassium,  sodium, 
ammonium,  barium,  and  strontium  are  soluble;  the 
oxides  of  calcium  and  arsenicum  are  soluble  with  difficulty, 
that  is,  require  relatively  a  large  amount  of  water  to  dis- 
solve a  small  amount  of  solid:  thus,  arsenous  oxide 
requires  from  30  c.  c.  to  80  c.  c.  of  cold  water  and  15  c.  c. 
of  boiling  water  to  dissolve  i  gramme  of  the  solid.  Try- 
to  dissolve  ferrous  sulphide  (used  in  making  sulphuretted 
hydrogen)  and  it  will  be  found  to  resemble  the  black 
oxide  of  manganese.  The  same  is  true  of  many  other 
sulphides,  but  those  of  sodium,  potassium,  ammonium, 
barium,  and  strontium  are  soluble  like  the  oxides  of  these 
same  elements.  The  sulphide  of  calcium,  likewise,  is 
soluble  with  difificulty. 

B.  Test  the  solubility  of  calcium  phosphate,  carbonate 
and  oxalate,  cupric  arsenite,  plumbic  chromate,  and  mag- 
nesium borate:  they  will  be  found  to  resemble  the  oxides 
and  sulphides. 

From  the  above  two  experiments  may  be  deduced  the 

following: 

Rule  for  Solubility. 

A  Chlorides,  iodides,  sulphates,  and  nitrates  of  the 
elements  are  soluble  in  water.  Exceptions: — plumbic, 
mercurous,  argentic,  antimonic,  and  chromic  chlorides, 
and  iodides;  barium,  strontium,  calcium,  plumbic,  bis- 
muthic,  mercuric,  and  antimonic  sulphates;  bismuthic 
nitrate.  N.  B.  Calcic  sulphate  is  slightly  soluble  in 
water. 

B.  Oxides,  sulphides,  carbonates,  phosphates,  arsen- 
ites,  chromates,  borates,  and  oxalates  are  insoluble  in 


384  DENTAL    CHEMISTRY. 

water.  Exceptions: — all  compounds  thus  far  mentioned 
of  potassium,  sodium,  and  ammonium  are  soluble  in 
water.  The  oxides  and  sulphides  of  barium,  and  stron- 
tium are  soluble  and  of  calcium  difficultly  soluble.  Cer- 
tain chromates  are  soluble,  as  those  of  magnesium,  man- 
ganese, and  iron  (ferric);  those  of  strontium  and  cal- 
cium are  difficultly  soluble.  The  oxalate  of  chromium 
(chromic)  is  soluble,  the  oxalates  of  iron  difficultly. 

Exercise  3.  Inorganic  substances  insol- 
uble in  water  but  soluble  in  acids:— 

A.  Put  a  very  little  calcic  carbonate  into  half 
a  test-tubeful  of  water,  shake,  and  it  does  not 
dissolve  but  makes  a  milky  liquid.  Now  add 
a  few  drops  of  hydrochloric  acid,  or  nitric  acid. 
Bubbling  takes  place  {effervescence)  and  the 
substance  dissolves.  Calcic  carbonate  is  in- 
soluble in  water  but  readily  soluble  (with 
effervescence)  in  hydrochloric,  or  nitric  acids. 
N.  B.  Care  must  be  taken  in  performing  this 
experiment  not  to  provoke  too  violent  efferves- 
cence by  addition  of  too  much  acid. 

B.  Test  thesolubility  in  acids  of  the  oxides  insoluble  in 
water  as,  for  example,  magnesium  oxide  or  magnesia, 
and  they  will  be  found  readily  soluble  in  hydrochloric  or 
nitric  acids,  except  those  of  chromium  ( — ic)  and  tin, 
which  are  soluble  with  difficulty.  Test  the  solubility  in 
acids  likewise  of  the  sulphides  insoluble  in  water  as,  for 
example,  ferrous  sulphide,  and  they  win  be  found  solu- 
ble in  hydrochloric  or  nitric  acics,  except  mercuric 
sulphide.  The  same  is  true  of  all  other  salts  mentioned 
under  Rule  B,  except  plumbic  chromate,  which  is  soluble 
with  difficulty  in  acids. 


EXPERIMENTAL    CHEMISTRY.  385 

N.  B.  In  some  of  the  tests  above  described  it  will  be 
necessary  to  use  undiluted  (concentrated)  acids. 

Exercise  4.  Inorganic  substances  insol- 
uble in  botli  water  and  acids. 

Test  the  solubility  of  barium  sulphate  and 
it  will  be  found  insoluble  in  both  water  and 
acids.  Calcium  sulphate  will  be  found  to  be 
soluble  with  difficulty  in  strong  acids;  so  also 
plumbic  chloride  and  iodide,  mercurous  chloride, 
chromic  chloride,  plumbic  chromate. 

Exercise  5.  Substances  insoluble  in 
water  but  soluble  in  alcohol. 

Place  in  each  of  two  test-tubes  a  small  piece 
of  ordinary  rosin.  Now  fill  one  tube  half  full 
of  waterand  the  other  half  full  of  alcohol.  No 
solution  takes  place  in  the  first  tube  but,  in 
the  second  tube,  after  a  time  some  of  the  rosin 
is  dissolved.  Now  pour  the  contents  of  the 
second  tube  into  the  first,  and  a  turbid  liquid 
results;  since  the  rosin  is  insoluble  in  alcohol 
diluted  with  water,  it  separates  out  into  a  finely 
divided  condition,  and  is  said  to  be  in  sitspen- 
sion,  as  it  does  not  settle  on  standing.  More- 
over the  rosin  is  said  to  be  precipitated,  from 
its  solution  in  alcohol,  by  the  water  in  which 
it  is  insoluble. 

Exercise  6.,  Natural  waters  contain  sub- 
stances in  solution:— 

A.     Bore  a  hole  through  a  cork,  insert  a  bent 


386 


DENTAL   CHEMISTRY. 


glass  tube  through  it,  and  fit  into  a  flask. 
Connect  the  end  of  the  glass  tube  by  rubber 
tubing  with  a  long,  straight,  glass  tube,  the 
end  of  which  is  above  a  dish.  Cover  the  long 
glass  tube  with  cloth  wet  with  cold  water.  Fill 
the  flask  less  than  half  full  of  hydrant  water  and 
boil. 

The  steam  given  off  by  boiling  condenses  to 
water  again  in  the  cool  glass  tube,  and  flows  out 
into  the  dish.  Water  thus  formed  is  said  to  be 
distilled,  and  the  process  is  called  distillatiofi. 
Continue  the  process  until  but  little  water  is  left 


in  the  flask,  then  either  set  the  flask  over  the 
water  bath  or  cautiously  use  a  very  small  flame, 
so  as  not  to  crack  the  flask,  until  all  the  water  has 
evaporated.  There  will  be  left  in  the  flask  a 
slight  whitish  residue,  known  as  residue  on  dis- 


EXPERIMENTAL   CHEMISTRY.  387 

tillation,  and  composed  chiefly  of  salts  of  lime 
and  magnesia  (calcium  and  magnesium)  con- 
tained in  solution  by  the  water. 

B.  Test  various  waters  in  this  way,  to  see 
which  is  freest  from  mineral  matters  in  solution. 

That  which  condenses  and  drips  kom  the  long, 
cool  tube  is  known  as  the  distillate  and  is  com- 
paratively free  from  impurities.    ( See  Water. ) 

By  distillation  a  volatile  or  easily  evaporated  liquid 
may  be  separated  from  a  less  volatile  or  non-volatile  one. 
For  the  distillation  of  large  quantities,  copper  stills  are 
used  with  head  and  condenser  of  tin,  or  large  glass  retorts. 
(Figure  37.) 

Exercise  7.  Sublimation:—  Place  at  the  bot- 
tom of  one  of  the  small,  hard  tubes  (ignition 
tubes)  previously  described,  a  little  arsenic,  in 
quantity  size  of  a  pea.  Heat,  and  the  powder 
gradually  disappears  as  vapor,  but  collects  again 
on  the  cooler  part  of  the  tube.  This  change  of  a 
solid  into  a  gas,  and  back  again  into  a  solid,  is 
called  suMimation,  and  the  solid  deposited  in 
the  upper  part  of  the  tube  is  termed  a  sublimate. 

Exercise  8.  Precipitation:— 

To  half  a  test  tube  full  of  the  argentic  nitrate 
solution,  already  made,  {Ex.i  B.)  add  a  drop 
or  two  of  hydrochloric  acid.  A  white  precipitate 
is  formed  which  settles  in  time  to  the  bottom  of 
the  tube.    Save  it  for  exercise  10. 

Exercise  9.  Chemical  Change  :~ 

Carefully  weigh  out  a  small  quantity  of  reduced 


388  DENTAL    CHEMISTRY. 

iron,  heat  it,  let  cool,  weigh  again,  and  it  will 
have  gained  weight.  It  has  changed  by  taking 
up  something  from  the  air  which  has  combined 
with  it.  Do  the  same  with  the  oxide  of  zinc;  it 
turns  yellow  but,  on  cooling,  is  the  same  as  be- 
fore, not  having  gained  weight.  It  underwent 
physical  change  merely. 

Exercise  10.  Circumstances  favoring 
chemical  change. 

A.  Set  the  test  tube  containing  the  precipitate 
obtained  in  experiment  8  in  direct  sunlight,  and, 
after  a  time,  it  will  become  violet-colored.  Try 
the  precipitation  experiment  again,  but  this  time 
wrap  tube  in  dark  cloth.  The  precipitate  will 
not  change  color.  This  experiment  illustrates  the 
influence  of  light  on  chemical  change.  (For 
equation  see  Exercise  22,  Reductioji. ) 

B.  The  influence  of  heat  on  chemical  change 
has  already  been  shown  by  exercise  9  first  part. 
Union  with  oxygen  is  chemical  change,  and 
this  is  favored  by  heat.  Bring  a  match  close 
to  a  hot  surface  and  it  is  inflamed,  at  a  longer 
distance  it  is  not.  This  shows  that  heat,  in  order 
to  bring  about  change  must  not  act  over  too  great 
a  dista7ice. 

C.  Mix  powdered  cupric  sulphate  with  potass- 
ic  ferrocyanide  on  a  piece  of  paper,  taking  care 
that  both  are  dry,  and  that  720  pressure  is  brought 
to  bear  in  mixing.     No  visible  change  takes  place. 


EXPERIMENTAL    CHEMISTRY.  389 

Now  rub  them  up  together  in  a  mortar,  and  a  red 
color  appears.  This  experiment  shows  that  m- 
timate  contact  favors  chemical  action. 

D.  Heat  to  redness  in  one  of  the  small,  hard 
tubes  some  ferrous  oxalate  and,  in  another,  some 
reduced  iron,  using  about  a  gramme  of  each. 
After  heating  invert  the  tubes:  from  the  one  or- 
iginally containing  the  oxalate  will  come  iron,  in 
so  finely  divided  a  state,  as  to  take  fire  spontan- 
eously as  it  falls  through  the  air,  combining  in 
other  words  rapidly  with  oxygen.  From  the 
other  tube  will  come  merely  an  iron  oxide,  which 
does  not  inflame. 

This  experiment  shows  that  physical  condition 
has  to  do  with  chemical  change,  iron,  in  condition 
of  the  finest  powder,  combining  more  rapidly  and 
quickly  with  oxygen  than  otherwise.  An  iron 
wire  heated  under  similar  circumstances  is  only 
superficially  coated  with  oxide. 

E.  IVlix  as  in  C  some  tartaric  acid  with  bicarbo- 
nate of  sodium.  Nothing  visible  happens.  Now 
pour  the  mixture  into  a  beaker  of  water,  and  effer- 
vescence at  once  takes  place. 

This  experiment  illustrates  the  influence  of 
solution  on  chemical  action.  Solution  is  a  con- 
dition in  which  bodies  come  into  more  intimate 
contact  with  one  another  than  is  possible  in  the 
case  of  the  finest  powder,  the  particles  of  the 
bodies  being  separated  and  diffused  among  those 
of  the  dissolving  liquid. 


390  DENTAL    CHEMISTRY. 

For  this  reason  we  use  reagents  in  solniion 
so  far  as  possible. 

Exercise  11.  Physical  solution  and  chem- 
ical solution:— 

A.  Dissolve  a  little  sugar  in  water.  Evap- 
orate carefully  to  dryness  over  the  water-bath, 
and  the  sugar  is  recovered  unchanged. 

This  experiment  shows  that  no  chemical 
change  took  place  when  the  sugar  was  dis- 
solved, for  we  get  it  back  with  the  same  taste 
and  properties  as  before  it  was  dissolved. 

B.  Next  dissolve  in  a  dish  some  of  the  copper 
of  a  cent  by  means  of  nitric  acid.  A  blue  liquid 
results.  Evaporate  to  dryness,  and  a  blue  solid 
is  obtained. 

This  experiment  illustrates  chemical  solu- 
tion', the  solid  obtained  on  evaporation  is  very 
different  from  the  copper  originally  in  the  cent. 
Chemical  change  has  taken  place. 

Exercise  12.  Clieniical  combination: — 

A.  Rub  together  in  a  mortar  a  quantity  of 
mercury  with  a  small  quantity  of  iodine,  adding 
a  little  alcohol  to  control  the  action  by  keep- 
ing down  the  heat. 

B.  Rub  together  a  quantity  of  mercury  with 
a  larger  quantity  of  iodine,  adding  a  little  alco- 
hol. 

The  above  experiments  illustrate  chemical  combination'. 
Mercury,  the  fluid  of  silver-like  appearence,  and  iodine,  a 
blue-black  solid,  combine  to  form  new  substances  totally 


EXPERIMENTAL    CHEMISTRY.  301 

unlike  either  mercury  or  iodine.  Notice  that  according 
to  the  proportio?is  used,  bodies  essentially  different  are  pro- 
duced, a  greenish  substance  being  formed  in  the  first  case, 
and  a  scarlet-red  one  in  the  second. 

The  substances  thus  formed  from  the  union  of 
elements  are  known  as  compounds,  and,  from  the 
union  of  two  elements,  binary  compounds. 

Moreover  the  same  two  elements  may  form  dif- 
ferent binary  compounds  according  to  the  pro- 
portions in  which  the  elements  are  used.  Under 
different  conditions,  then,  the  same  two  elements 
form  different  compounds. 

The  combinations  illustrated  above  are  examples 
of  what  are  known  as  direct  combinations. 

Exercise  13.  Decomposition  of  Compounds: 
— A.  Place  some  mercuric  oxide  in  an  ignition 
tube,  provided  with  a  cork  through  which  passes 
a  bent  deliveiy  tube  dipping  under  water;  invert 
over  the  end  of  the  delivery  tube  a  test-tube 
filled  with  water.  Heat  the  ignition  tube  to  red- 
ness and  collect  the  gas  given  off  in  the  inverted 
test-tube.  Notice  the  sublimate  on  ignition  and 
deliveiy  tubes. 

This  experiment  illustrates  the  decomposition,  or  break- 
ing up,  of  a  binary  compound  into  its  constituent  ele- 
ments by  heat.  Mercuric  oxide,  the  solid  is  decomposed 
by  heat  into  metallic  mercury,  which  is  the  sublimate  on 
the  tube,  and  oxygen,  which  is  the  gas  bubbling  up  under 
water.  Recognition  of  the  oxygen  may  be  undertaken 
by  the  means  employed  in  the  experiments  on  Oxygen, 
which  see. 


392  DENTAL    CHEMISTRY. 

B.  Heat  a  piece  of  zinc  amalgam  in  a  tube  and  collect 
the  mercury  given  off. 

C.  Heat  some  limestone  in  a  crucible  over  the  blow-pipe 
flame.  It  is  decomposed  into  lime  and  carbonic  acid, 
thus: — 

CaC03  =  CaO+C02 
Limestone  (calcium  carbonate)  is  a   ternary  compound 
containing  three  elements,  and  is  decomposed  by  heat 
into  two  binary  ones,  calcium  oxide  and  carbonic  oxide, 
the  former  being  a  white  solid,  the  latter  a  gas. 

D.  Decomposition  by  light  has  already  been  shown  in 
exercise  lo.  A. 

E.  Pass  an  electric  current  through  water.  It  is  decom- 
posed into  its  two  elements,  hydrogen  and  oxygen.  (This 
experiment  will  be  shown  in  full  further  on.) 

Exercise  14.  Direct  decomposition  by 
mutual  action  of  substances  on  eacli  otlier: 

Put  a  few  pieces  of  zinc  into  a  flask,  and  then 
add  diluted  sulphuric  acid.  The  zinc  is  dis- 
solved, hydrogen  gas  given  off,  and  zinc  sulphate 
formed. 

This  experiment  illustrates  the  direct  decomposition  of 
the  acid  by  the  zinc  as  follows: — 

Zn-FHgSO^^ZnSO^+Ha 
The   experiment  may  be   omitted  here  as  it  will  be  per- 
formed in  exercise  25,  when  reference  to   this  exercise 
should  be  made. 

Exercise  15.   Double   Decomposition:— A. 

Dissolve  some  calcium  chloride  in  water  in  a 
beaker;  in  another  beaker  dissolve  some  sodium 
carbonate.  Mix  the  two  and  a  white  precipitate  is 
formed. 


EXPERIMENTAL    CHEMISTRY.  393 

This  experiment  shows  that  two  substances  soluble  in 
water  may  produce  a  third  substance  quite  insoluble  in 
water. 

Calcium  chloride  and  sodium  carbonate,  both  soluble, 
produce  calcium  carbonate  (chalk)  and  sodium  chloride 
(common  salt.)     The  equation  is  as  follows: 

CaCl2  +  Na2C03  =  CaC03+2NaCl 
Decomposition  of  this  kind  is  known  as  double  decomposi- 
tio7i,  the  general  rule  for  which  has  been  already  given. 
(See  Berthollet's  laws.) 

B.  In  Exercise  3  there  is  double  decomposition,  hydro- 
chloric acid  and  calcium  carbonate  forming  calcium  chlor- 
ide and  carbonic  acid,  thus: — 

2HCl-fCaC03  =  CaCl2-|-C024-H20 
One  very  practical  application  of  the  law^s  of  chemical 
decomposition  is  to  be  found  in  pharmacy  where  solutions 
are  so  often  to  be  mixed.     The  following  rules*  will  aid 
the  pharmacist: — 

1.  Two  salts  in  solution  may  form,  by  the  interchange 
of  their  acids  and  bases,  tA^o  insoluble  salts,  which  are 
precipitated. 

2.  When  two  salts  in  solution  form,  by  the  interchange 
of  their  acids  and  bases,  a  soluble  and  an  insoluble  salt, 
the  latter  will  generally  be  precipitated,  or  may  form  with 
the  soluble  salt  a  double  salt. 

Given  two  clear  solutions,  one  of  barium  chloride  and 
the  other  of  sodium  sulphate.  On  adding  one  to  the  other 
a  copious  precipitate  is  formed;  this  is  insoluble  barium 
sulphate.  Filtering  the  clear  liquid,  we  find  it  to  be  a 
solution  of  sodium  chloride. 

3.  When  two  salts  in  solution  do  not  give  rise  to  an 
insoluble  salt  no  precipitate  will  result,  though  there  may 
be  decomposition. 

4.  An  acid  will  decompose  a  salt: 

♦Griffith 


394  DENTAL    CHEMISTRY. 

a.  If  the  acid  added  be  more  fixed  or  more  soluble 
than  that  of  the  salt. 

b.  If  the  acid  added  can  form  an  insoluble  or  a  less 
soluble  compound  with  the  base  of  the  salt. 

c.  If  the  acid  added  possesses  a  greater  affinity  for  the 
base  of  the  salt. 

d.  If  the  acid  of  the  salt  be  gaseous. 

5.  Oxides  of  the  alkalies  decompose  salts  of  the  metals 
proper  and  of  the  alkaloids,  and  precipitate  their  bases, 
or  the  base  may  be  soluble  in  excess  of  the  alkali. 

Given  a  solution  of  sulphate  of  zinc.  If  a  little  liquor 
potassae  be  added  to  it  a  precipitate  of  oxide  of  zinc  will 
result;  and  on  adding  more  of  the  liquor  potassae,  the 
precipitate  becomes  dissolved. 

6.  Metallic  oxides  combine  with  acids  to  form  salts, 

7.  Vegetable  substances  containing  tannic  or  gallic 
acids  precipitate  albumin  vegetable  alkaloids,  and  most 
of  the  metallic  oxides,  and  form  with  salts  of  iron  inky 
solutions.  Substances  containing  tannic  acids  also  prec- 
ipitate gelatin. 

8.  Many  glucosides  are  incompatible  with  free  acids  or 
emulsions. 

Exercise  16.  Nascent  State:— Warm  a  piece 
of  gold  leaf  in  chlorine  water.  No  visible  solu- 
tion takes  place.  On  the  other  hand  mix  40  c.c. 
of  nitric  acid  with  180  c.  c.  of  hydrochloric,  fill  a 
test-tube  half  full  of  the  mixture  and  add  gold 
leaf.  Warm  the  mixture.  The  gold  rapidly  dis- 
solves. 

This  experiment  shows  that  gold  is  soluble  in  chlorine 
'wi  the  nascent  state  dJi  it  is  called.  The  mixture  of  acids 
mentioned  above  sets  chlorine  free  which,  when  just  set 
free,  has  energy  enough  to  combine  with    gold,  forming 


EXPERIMENTAL    CHEMISTRY.  395 

auric  chloride.     But  a  solution  of  chlorine  in  water  already- 
made  is  without  action  on  the  gold. 

The  expression  nascent  state  is  used  of  elements  at  the 
moment  when  their  atoms  leave  molecules,  and  have  not 
yet  had  time  to  re-enter  into  combination.  In  this  state 
the  atoms  have  much  greater  energy  to  combine  than 
after  having  entered  into  a  combination  with  other  atoms 
of  either  the  same  kind  or  of  another  kind. 

Exercise  17.    The  properties  of  acids;— 

Take  any  acid  at  the  desk  and  dilute  it 
with  water,  1  part  of  acid  to  10  of  water.  Notice 
that  it  has  the  following  properties: — 

A.  Acid  or  sour  taste. 

B.  Changes  the  color  of  many  vegetable  sub- 
stances, as  litmus  from  blue  to  red. 

C.  Contains  hydrogen.  (This  experiment  may 
be  omitted  till  hydrogen  is  taken  up,  exercise  25.) 

D.  It  attacks  various  metals  as  tin,  lead,  silver, 
copper,  especially  when  heated  with  them.  Un- 
diluted it  burns  and  stains  the  skin  and  clothing. 

E.  All  acids  are  not  liquids.  Examine  glacial 
phosphoric  acid  for  example. 

Exercise  18.  The  properties  of  bases  or 
hasic  substances:— 

Take  any  hydroxide  at  the  desk  as,  for  example, 
solution  of  sodium  hydroxide.  Dilute  it  with 
water  1  to  10.  Note  that  it  has  the  following 
properties: — 

A.  The  taste  of  lye  or  an  alkaline  taste. 

B.  A  soapy  "feel"  when  rubbed  between  the 
fingers. 


396  DENTAL    CHEMISTRY. 

C.  Restores  the  color  of  organic  substances, 
changed  red  by  acids,  to  blue. 

D.  When  acted  on  by  an  acid  forms  a  neutral 
substance. 

Dilute  5  c.  c.  of  hydrochloric  acid  by  adding  say  20  c.c. 
of  water  to  it  and  pour  into  a  burette.  Underneath  the 
burette  set  a  beaker  containing  5  c.  c.  of  sodium  hydrox- 
ide. Drop  into  it  a  slip  of  litmus,  which  is  at  once  turned 
blue.  Now  let  the  dilute  acid  drop  in  from  the  burette, 
drop  by  drop,  until  a  faint  red  color  shows  on  the  litmus. 
Evaporate  the  liquid  to  dryness  and  note  salty  taste  of 
residue,  which  is  common  salt: — 

NaH0+HCl  =  NaCl+H20 
Dry  the  residue  and  it  will   when   dissolved   in   distilled 
water  affect  neither  litmus  paper  being  neutral   in  reac- 
tion. 

E.  Next  neutralize  sulphuric  acid  with  magnesia  and 
note  bitter  taste  of  the  residue,  magnesium  sulphate  being 
formed: — 

H2S04  +  MgO  =  MgS04+H20 

F.  Strong  solutions  of  the  bases  are  corrosive, 
burn  the  clothing,  face,  and  hands.  Vinegar  or 
dilute  acetic  acid  may  be  used  to  counteract  their 
influence.  Ammonium  hydroxide  is  very  de- 
structive to  the  eyes,  and  the  vapor  of  concentrated 
ammonia  water  is  dangerous. 

Substances  having  neither  acid  nor  basic  properties  are 
called  neutral  and  are  very  numerous.  Water  is  an  exam- 
ple, also  common  salt,  silver  nitrate,  and  a  host  of  other 
substances, 


CHAPTER  VII. 

PRACTICAL     CHEMISTRY      OF       THE,     ELEMENTS    AND     THEIR 
INORGANIC     COMPOUNDS. 

In  this  chapter  the  non-metals  and  their  compounds 
will  be  considered  first,  followed  by  the  metals.  Reac- 
tions characteristic  of  elements  and  compounds  will  be 
given  in  the  chapter  on  Chemical  Analysis,  this  chapter 
being  devoted  entirely  to  experimental  work. 

Exercise  19.  Oxygen:  Heat  five  grammes  of 
potassium  chlorate  in  a  dry  flask  holding  about 
1 00  c.  c.  (3  fl.  oz.).  The  flask  should  be  provided 
with  a  perforated  cork  through  which  runs  a 
bent  glass  tube  (fig.  38)  leading  under  the  sur- 
face of  water.  The  chlorate  after  a 
time  melts,  and,  on  further  heating, 
effervesces,  When  the  presence 
of  gas  in  the  water  is  shown  by 
bubbling,  fill  a  large  test-tube  full 
of  water,  and  invert  it  over  the 
mouth  of  the  delivery  tube.  Gas 
rises,  and  displaces  the  water  in 
'pig.  38.         the  tube.      In  this  way  collect 

several  test-tubes  full  of  gas.    Take  the  end  of 

397       . 


398  JJENTAL    CHEMISTRY. 

the  delivery  tube  from  the  water,  before  with- 
drawing the  flame.  Apply  alighted  taper  to  one 
of  the  tubes  full  of  oxygen,  and  observe  that  the 
gas  will  not  burn,  but  that  the  taper  burns  more 
brilliantly  than  in  air.  Blow  out  the  flame  of  the 
taper  leaving  the  end  of  it  still  glowing,  and  again 
plunge  it  into  another  tube  full  of  oxygen.  Notice 
that  it  is  re-ignited. 

Oxygen  is  incombustible,  but  is  an  active 
supporter  of  combustion. 

Oxygen  may  be  made  on  a  large  scale  in  a  riietallic  re- 
tort (fig,  39)  by  using  a  mixture  of  four  parts  potassic 
chlorate  and  one  part  manganese 
dioxide.-  The  object  of  the  mixture 
is  to  obtain  the  gas  at  a  lower  tem- 
perature, and  without  fusing  the 
chlorate.  No  change  takes  place  in 
the  manganese  dioxide,  and  the  ex- 
act action  is  not  understood. 
Fig.  39.  Oxygen,   for    use    in  therapeutics 

and  commerce,  is  produced  at  low  cost  by  the  Brin  pro- 
cess, which,  as  now  perfected,  consists  in  heating  a  porous 
barium  oxide  to  700°  C.  in  closed  vertical  retorts,  into 
which  purified  air  is  forced  under  a  pressure  of  ten  or  fif- 
teen pounds  more  than  that  of  the  atmosphere.  Barium 
peroxide  is  formed,  and,  when  the  air  pressure  is  reduced 
to  fourteen  pounds  below  atmospheric,  oxygen  is  rapidly 
given  off. 

Exercise  20.    Oxidation  and  reduction:— 

Hold  some  zinc  turnings  in  the  Bunsen  flame 
using  the  tongs.  Notice  that  they  ignite,  and 
turn  into  a  white  powder  which  is  zinc  oxide.  The 


EXPERIMENTAL    CHEMISTRY.  399 

addition  of  oxygen  to  the  zinc  is  called  oxidation. 
The  oxygen  added  to  the  zinc  is  derived  from  the 
air.  The  equation  is  as  follows: 
Zn+0=Zn  O. 
Now  place  a  small  quantity  of  silver  oxide  in 
one  of  the  small,  hard,  ignition  tubes  and  heat 
gently.  A  bright  mass  of  silver  is  formed.  The 
oxygen  of  the  oxide  is  set  free,  and  the  silver  is 
reduced,  as  the  term  is.  The  removal  of  oxygen 
from  any  compound  is  called  reduction. 

Exercise  21.    Equations  illustrating  oxidation : — 

The  class  at  this  point  should  consider  various  equations 
illustrating  oxidation.  The  oxygen  may  be  derived  either 
from  the  air  or  from  oxidizing  agents,  as  nitric  acid,  as 
follows: 

C+02  =  C0, 
.  P,+05  =  P,05 
2FeO+0=Fe203 
H2S+202  =  H2S64 
2H2S+02=2H20+S2 
2Cu2  0+02=4CuO 
FeS04+2NaHO=Na2S04+Fe2(HO)2 

and 
2[Fe2(HO)2]+0+H20=Fe2(HO)6 
N.  B.  The  above  equation  illustrates  the  formation  of 
io-xxous  hydroxide  and  the  oxidation  of   it  into  iexxic  hy- 
droxide. 

3PbS+8HN03  =  3PbS04+8NO+4H20 
N.  B.    The   above   equation   shows  the    oxidation  of 
metallic  sulphides  into  sulphates  by  strong  acids  (oxygen 
containing  bodies).     No  sulphur  separates  in  this  case. 
Hg2Cl2+2Cl=2HgCl2 
N.  B.  In    the  above  equation   the  mercur6V«    chloride 


400  DENTAL    CHEMISTRY. 

Hga  Cl^  is  said  to  be  "oxidized"  by  chlorine  into  mer- 
curic  chloride.  The  term  oxidation  is  thus  sometimes 
broadly  used  to  denote  change  from  an  — ous  compound 
(lower)  to  an  — ic  one  (higher). 

Some  common  oxidizing  agents  are  potassium  chlorate, 
chromic  acid,  nitric  acid,  chlorine,  iodine,  potassium  di- 
chromate,  potassium  ferricyanide,  and  manganese  dioxide. 
Mn02+4HCl=MnCl,+2H20+Cl2 

In  the  above  equation  the  hydrogen  of  the  HCl  is  oxi- 
dized by  the  oxygen  of  the  MnO.j,  water  being  formed 
and  chlorine  set  free.     See  exercise  40. 

In  the  act  of  oxidation  the  substances  formed  are 
called  oxides.  There  are  three  classes  of  oxides,  namely, 
basic  oxides,  neutral  or  indifferent  oxides,  and  acid-form- 
ing oxides  also  called  anhydrides. 

Basic  oxides  are  those  which  plus  water  yield  bases 
(hydroxides)  thus  K20+H20  =  2KHO.  They  neutralize 
acids  and  with  them  form  salts  as  K204-H2S04=K2S04 
-j-HgO.  Neutral  or  iiidifferent  oxides  are  those  which  yield 
neither  bases  nor  acids  with  water;  examples  MnOa.PbO.,. 

.^w/y/^n'^^.?  are  those  which  plus  water  yield  acids;  ex- 
amples SOs.NA.    Thus  SOg-f  HoO  =  H2SO,. 

The  more  common  basic  oxides  are  K^O,  NagO,  CaO, 
BaO.  Basic  oxides,  insoluble  in  water,  yet  serving  to  neu- 
tralize acids  and  to  form  salts,  are  AlaOg.PbO.MnO.CuO. 
Thus  AloOg  neutralizes  sulphuric  acid  and  forms  a 
salt  with  it,  according  to  the  equation: — 

Al,03-f3H,Sp,  =  AL(SOj3+3H20 
As  a  rule  the  fewer  the  oxygen  atoms  the  more  basic 
the  oxide;  thus,  of  the  four  oxides  of  manganese,  MnO  is 
strongly  basic,  Ma.Og  weakly  basic,  MnOa  indifferent,  and 
MnOg  an  anhydride.  Some  common  neutral,  or  in- 
different oxides  are   MnO„  HoO.PbO,. 


EXPERIMENTAL  CHEMISTRY.  401 

The  more    common  anhydrides   are  SO2,  SO3,  P2O3, 

P,0„        CIA  Cl^Og.Cl.Og*         Cl.O,*  N.Og,         N.Og,        I,0  g  , 

As  0O3,  As  2O5,  SbaOg,  CO2,  Cr03,  SiOa.  The  last  is  in- 
soluble in  water  yet  forms  salts  when  treated  with  hydrox- 
ides, thus  Si02+2KHO=K2Si03+H20. 

Anhydrides  are  oxides  of  negative  elements,  but  all  ox- 
ides of  negative  elements  are  not  anhydrides;  thus,  there 
are  three  oxides  of  the  negative  element  chlorine,  an  d 
four  acids  containing  it,  namely  chlorine  monoxide  CI2O, 
chlorine  trioxide  CI2O3,  and  chlorine  peroxide  CI2O4; 
also  hypochlorous  acid  HCIO,  chlorous  acid  HCIO2,  chlor- 
ic acid  HClOg.and  perchloric  acidHC104.  The  monox- 
ide and  trioxide  then  are  anhydrides,  since  by  adding  H2O 
to  their  formulae  those  of  the  first  two  acids  are  obtained. 
But  chlorine  peroxide  does  not  form  any  of  the  four 
acids  on  addition  of  water,  nor  have  the  anhydrides,  cor- 
responding to  these  acids,  ever  been  isolated.  Therefore 
chlorine  peroxide  is  not  an  anhydride.  Again  there  are 
five  oxides  of  nitrogen,  namely  nitrogen  monoxide  NgO, 
nitrogen  dioxide  N202=2(NO),  nitrogen  trioxide  N2O3, 
nitrogen  tetroxide  N204=2(N02),  and  nitrogen  pentox- 
ide  N2O5.  Of  these  the  first,  third,  and  fifth  are  anhy- 
drides, combining  with  water  to  form  hyponitrous,  nitrous, 
and  nitric  acid  respectively,  but  the  second  and  fourth  are 
not  anhydrides. 

Exercise  22:— Equations  illustrating  re- 
duction:— 

CuO+heat  +H,=Cu+H20 
Note: — this  equation  illustrates  the  reduction  of  a  me- 
tallic oxide  by  hydrogen.      Most-ofthe  metallic  oxides  are 
reduced  at  a  red  heat  by  hydroge?!. 

Fe203+3H2=Fe2-f-3H20 
Iron  thus  formed  is  known  as  reduced  or  Quevenne's  iron. 


*Not  in  separate  state. 


402  DENTAL    CHEMISTRY. 

FeoCl6+Zn=2FeCl2+ZnCl2 
This  equation  illustrates  reduction  by  zinc. 
2Fe203+3C2=2Fe2+6CO 
CaSO,+2C=CaS+2C02 
2  As  203+3C=4  AS+3CO2 
The  above  three  equations  illustrate  reduction  by  car- 
bon SO  often  used  in  metallurgy. 

Other  equations  illustrating  reduction: — 
2HgO+heat=Hg2+02 
Fe2Clo+H,S=2FeCl2+2HCl4-S 
Cu3+8HN03=3Cu(N03)2+4H20+N.A 
2AgCl+light=Ag2Cl+Cl 
The  term  reduction  is  now  also  used  to  signify  removal  of 
a  negative  element,  thus,  i&rvic  chloride  under  certain  cir- 
cumstances is  said  to  be  "reduced"  to  ierrotis. 

Reducing  agents  are  sulphurous  acid,  sodic  hyposul- 
phite, oxalic  acid,  ferrous  oxide,  arsenous  anhydride, 
stannous  chloride,  potassium  ferrocyanide,  and  zinc,  or 
magnesium. 

Carbon  and  carbon  monoxide  are  used  as  reducing 
agents  in  metallurgy. 

Glucose  is  an  example  of  an  organic  reducing  agent. 
Organic  reducing  agents  will  be  discussed  under  the  head- 
ing of  Organic  Chemistry. 

Exercise  23.  Hydric  Dioxide:— 

A.  Take  the  reaction  of  a  sample  of  commercial 
**  peroxide,"  as  it  is  called  and  notice  that  it  is 
strongly  acid. 

Acids  in  small  quantities  are  added  to  it  in  order  to  pre- 
vent decomposition,  as  follows:  2H202=2H.,0+0^,  oxy- 
gen being  readily  given  off. 

B.  Obtain  some  pus  from  a  suppurating  surface 
and  add  to  it  a  little  of  the  peroxide.    Notice  the 


EXPERIMENTAL    CHEMISTRY.  403 

"foaming"  or  effervescence,  oxygen  gas  being 
given  off.  Try  the  same  experiment  in  the  mouth, 
in  a  suppurating  cavity. 

C.  Show  the  bleaching  properties  of  hydric 
dioxide  by  adding  it  in  excess  to  a  solution,  say, 
of  logwood  which  has  been  rendered  alkaline  by 
a  few  drops  of  ammonia  water. 

D.  Show  its  action  in  decolorizing  perman- 
ganate by  adding  it  to  a  solution  of  the  latter, 
acidified  with  sulphuric  acid.  Oxygen  is  evolved 
as  follows: — 

5H202+2KMn04+3H2SO,=8H20+2MnSO,+K2SO,+Oio 

E.  Show  the  method  by  which  it  is  prepared 
by  mixing  in  a  test  tube  20  drops  of  sulphuric 
acid  and  3  c.c.  of  water.  Also  mix  a  little  piece 
of  baric  dioxide,  BaOa ,  with  enough  water  to 
make  a  thick  paste,  using  a  dish.  Take  up  with 
a  glass  rod  small  portions  of  this  paste,  and  dip 
them  into  the  tube  containing  the  dilute  H2  SO^. 
Keep  the  tube  cool,  by  immersing  it  in  a  larger 
vessel  containing  ice  water.  The  equation  is  as 
follows:   BaO,+H2SO,=BaS04+H,03. 

F.  Medical  and  dental  students  should  note  the  require- 
ments of  the  United  States  Pharmacopceia  with  reference 
to  hydrogen  dioxide  as  follows:  There  should  be  no 
hydrofluoric  acid  in  it,  barium  should  be  absent,  and 
50  c.c.  of  it  should  not  require  more  than  0.5  c.c.  of  potas- 
sium hydrate  (volumetric  solution)  to  render  it  alkaline. 

Exercise  24.  Ozone:— 

A.  Gradually  add  baric  dioxide  in, small  por- 


404  DENTAL    CHEMISTRY. 

tions  to  a  little  cold  sulphuric  acid  undiluted. 
Oxygen  is  given  off  which  is  tolerably  rich  in 
ozone: 

3  H,SO,+3BaO,= 

3  BaSO,+3H,0+03 

B.  Note  the  peculiar  odor  of  ozone,  penetrat- 
ing, chlorine-like  (or  phosphorus)  odor,  and  its 
action  on  potassium-iodide-starch  paper,  which 
is  colored  blue. 

C.  Note  that  hydric  dioxide  also  turns  the 
potassium-iodide-starch  paper  blue  but  that 
ozone,  in  addition,  blackens  bright -strips  of  silver 
foil. 

A  complete  apparatus  for  the  generation  of  ozone  with 
baric  dioxide  and  sulphuric  acid  may  be  purchased  ready 
made. 

Exercise  25.    Hydrogen:— 

A.  Make  hydrogen  gas  by  placing  about  10 
grammes  of  granulated  zinc  in  a  flask  of  about 
200  c.c.  capacity,  provided  with  a  twice  perforated 
cork  or  rubber  stopper,  through  which  are  in- 
serted two  tubes,  one  a  straight  (thistle)  tube, 
the  other  a  bent  tube.  The  thistle  tube  goes 
nearly  to  the  bottom  of  the  flask,  the  bent  tube 
only  a  short  distance  through  the  cork.  Cover 
the  zinc  in  the  flask  with  water,  insert  the  stopper 
with  its  tubes,  and  pour  into  the  thistle  tube  a 
little  sulphuric  acid,  adding  more  from  time  to 
time  when  evolution  of  gas  ceases.  Efferves- 
cence takes  place  around  the  zinc.    Collect  the 


EXPERIMENTAL    CHEMISTRY.  405 

gas  over  water  as  usual  in  several  test-tubes,  and 
reserve  for  further  experiments.  The  equation 
has  already  been  given,  page  392. 

B.  Remove  the  first  test-tube  of  gas,  mouth 
downward,  to  a  flame  near  by.  An  explosion 
takes  place,  showing  that  hydrogen  mixed  with 
air  driven  off  from  the  flask  is  explosive. 

C.  Repeat  the  experiment  with  the  second  or 
third  tubes,  and  notice  that  hydrogen  not  mixed 
with  air  burns  quietly,  but  that  if  a  taper  is  pushed 
up  into  the  tube  the  flame  is  extinguished. 

Hydrogen  is  combustible  but  does  not  sup- 
port combustion. 

D.  Hold  another  tube  filled  with  gas  mouth 
upwards  for  a  few  moments  and  notice  that  the 
gas  escapes,  hence  is  lighter  than  air.  That 
the  gas  escapes  may  be  proved  by  igniting  it 
it  above  the  tube  and  noting  absence  of  ignition 
in  the  tube. 

E.  After  a  time  ignite  the  gas  directly  at  the 
mouth  of  the  ignition  tube  whence  the  hydrogen 
was  derived,  and  notice  that  it  burns  with  a  color- 
less flame. 

F.  Evaporate  to  dryness  the  liquid  in  the  flask 
after  the  experiment  is  concluded  and  notice  that 
a  salt-like  substance  in  ciystals  is  obtained.  This 
is  zinc  sulphate.  The  equation  of  its  formation 
has  already  been  given. 


406  DENTAL    CHEiMISTRY. 

Exercise  26.    Water:— 

A.  Show  that  water  is  a  compound  of  hydro- 
gen and  oxygen  by  decomposition  with  electricity. 
Two  tubes,  (Fig.  40)  closed  at  one  end  and 
filled  with  water,  are  suspended 
vvith   their  mouths  beneath  the 
surface  of  some  water  acidulated 
with  sulphuric  acid,  contained  in 
a  glass  dish  below.    Through  the 
sides  of  this  dish  pass  two  wires, 
each  terminating  in  a  plate  of  plat- 
inum seen  beneath  the  open  ends 
of  the  tubes.   On  connecting  these 
Fig.  40.  wires  with  a  battery,  (Grove's)  of 

6  or  8  cells,  a  torrent  of  gas-bubbles  rises  from 
each  platinum  plate  into  the  tube  above  it.  Notice 
that  the  tube  over  the  negative  electrode  tills 
twice  as  rapidly  as  the  other;  test  the  gas  in  each, 
when  the  tubes  are  both  filled,  and  note  that  the 
gas  in  this  tube  is  hydrogen  while  that  in  the 
other  is  oxygen.  In  other  words  water  contains 
2  volumes  of  hydrogen  to  1  volume  of  oxygen. 
Since  oxygen  is  16  times  heavier  than  hydrogen 
the  ratios  by  weight  are  as  2:16  or  as  1 :8;  that  is, 
water  is  composed  of  88.89  per  cent,  of  oxygen, 
and  11.11  per  cent,  of  hydrogen. 

The  apparatus  for  electrolytic  decomposition  of   water 
can  now  be  had  ready  made  at  a  small  cost. 


EXPERIMENTAL    CHEMISTRY.  407 

B.     Show  that  water  is  formed  by  the  union  of 
oxygen  and  hydrogen  by  use  of  Ure's  eudiometer. 
(Fig.  41).    This  is  simply  a  glass  U- 
tube  closed  at  one  end,  this  end  being 
graduated  and  also  pierced  near  its  ex- 
tremity by  two  platinum  wires.    Fill  this 
limb  with  water,  and  then  introduce  20 
c.c.  of  pure  oxygen  from  a  delivery-tube 
and  then   40  c.c.  of  hydrogen.     Make 
the  measurements  when  the  level  of  the 
liquid  is  the  same  in  both  limbs.    Then 
close  the  open  end  with  the  thumb,  leav- 
ing a  cushion  of  air  between  it  and  the 
Fig-  41      water,  and  pass  a   spark  through  the 
mixed  gases  by  means  of  the  platinum  wires.    A 
slight  flash  appears  on  the  passage  of  the  spark, 
and  suction  is  immediately  felt  by  the   thumb. 
Remove    the  latter  carefully,  fill  the  open   lim.b 
with  the  additional  amount  of  water  necessary, 
and  the  gases  in  the  closed  limb  will  be  found  to 
have  disappeared,  in  other  words  20  volumes  of 
oxygen  have  united  with  40  of  hydrogen  to  form 
water. 
Exercise  27.  Nitrogen :— 
A.  For  preparation  of  nitrogen  use  the  same 
apparatus  as  that  employed  for  oxygen.     Place 
in   the  flask  about  10  grammes  of  potassium 
nitrite,  and  almost  an  equal  weight  of  ammonium 
chloride.     Add  water,  sufficient  to  dissolve  the 
solids   and  apply  heat  which  must  be  well-regu- 


408  DENTAL    CHEMISTRY. 

lated  or  else  too  violent  evolution  of  gas  will  take 
place.    The  equation  is  as  follows: — 
KN0,+NH,C1— KC1+N,+2H,0 

B.  Collect  the  gas  in  test-tubes,  as  in  case  of 
oxygen,  and  show  that  it  is  neither  combustible 
nor  a  supporter  of  combustion,  using  taper  as  be- 
fore. 
Exercise  28.  The  Air:— 
A.  Show  that  the  air  is  a  mixture  essentially 
of  nitrogen  (four- fifths)  and  oxygen  (on^-fifth) 
by  placing  a  graduated  glass  tube,  containing  a 
measured  volume  of  air,  mouth  downward  in  a 
dish  containing  mercury.  Introduce  a  small  ball 
of  phosphorus  on  the  end  of  a  wire,  and  let  it  re- 
main in  contact  with  the  air  for  several  hours, 
when  it  will  gradually  combine  with  the  oxygen, 
and  the  mercury  will  rise,  to  fill  the  space  pre- 
viously occupied  by  the  oxygen.  Knowing  the 
original  volume  of  the  air,  the  loss  in  volume  rep- 
resents oxygen,  and  the  volume  remaining  is 
chiefly    nitrogen. 

B.  Show  that  the  air  contains  some- 
thing else  besides  these  two  gases,  by 
passing  a  measured  volume  of  it  through 
two  U-shaped  glass  tubes  (fig.  42)  the 
one  filled  with  calcium  chloride,*  the  other 
with  potassium  hydroxide,  each  tube  and 
^'^'  *^'  contents  having  been  weighed  separately. 
After  the  experiment  is  over  it  will  be  found  that 

♦These  substances  should  be  in  solid  form,  not  in  liquid. 


n 


n 


EXPERIMENTAL    CHEMISTRY.  409 

each  tube  has  gained  in  weight,  the  one  contain- 
ing calcic  chloride  retaining  all  the  moisture  in 
the  air,  on  account  of  the  affinity  of  this  substance 
for  water,  and  the  other  all  the  carbon  dioxide. 

For  determining  the  precentage  of  carbon  dioxide  and 
moisture  in  air  with  accuracy,  expensive  apparatus  is 
required. 

Exercise  29.  Compounds  of  Nitrogen:— 

I.  Ammonia. 

A.  Prepare  ammonia  gas,  NH3,  by  mixing  equal 
weights,  about  10  grammes  each,  of  slaked  lime 
(calcic  hydroxide)  and  sal  ammoniac  (ammonium 
chloride)  in  a  flask  of  200  c.c.  capacity  and  cov- 
ering with  water.  Set  the  flask  on  an  asbestos 
sheet.  Insert  into  its  mouth  a  perforated  stopper, 
carrying  a  bent  tube  dipping  under  water.  Apply 
heat.  Ammonia  gas  is  given  off  according  to  the 
equation. 

2(NH,Cl)+Ca(HO),=CaCl,+2H,0+2NH3 
Note  the  odor,  and  the  alkaline  reaction  on  lit- 
mus of  the  water  in  which  the  gas  is  dissolved. 

B.  Take  the  mouth  of  the  bent  tube  out  of 
water,  connect  it  by  rubber  tubing  to  another 
glass  tube,  turn  the  latter  upwards,  and  hold  an 
empty  test-tube  over  it.  After  a  few  minutes 
withdraw  the  test-tube  and,  holding  it  mouth 
down,  place  in  a  vessel  of  water.  The  ammonia 
gas  in  the  test-tube  is  rapidly  absorbed,  and  the 
level  of  the  water  rises  at  once  to  the  top  of  the 


410  DENTAL    CHEMISTRY, 

tube,  ammonium  hydroxide  being  formed  accor- 
ding to  the  equation 

NH3+H30=NH,HO 

Note.  By  removing  the  test-tube  from  the  water,  when 
the  latter  has  risen  about  a  quarter  of  an  inch,  corking 
quickly,  and  shaking  well  a.  stronger  solution  oi  ammonium 
hydroxide  is  obtained,  which  responds  to  the  tests  for  bases 
already  given.  After  this  has  been  shown  bring  an  un- 
corked bottle  of  hydric  chloride  (hydrochloric  acid) 
near  to  it,  and  note  the  dense  white  fumes.  Put  a  drop 
of  each  in  a  watch-glass,  invert  over  one  another,  and  note 
the  white  solid  formed.  This  last  experiment  shows  that 
ammonia  gas  is  always  given  off  from  strong  solutions 
of  the  hydroxide,  and  that  it  unites  with  the  chlorine  of 
the  hydrochloric  acid  to  form  ammonium  chloride  accord- 
ing to  the  equation 

HC1+NH3  =  NH4C1 

II.  Nitrogen  Monoxide  or    Laughing    Gas 
(Nitrous  Oxide.) 

Place  in  the  same  apparatus  used  for  generat- 
ing oxygen  about  10  grammes  of  ammonium 
nitrate,  without  water.  Instead  of  a  bent  tube 
leading  under  water  one  leading  through  a  per- 
forated card  or  paper,  placed  on  top  of  a  beaker 
or  tumbler,  will  do.  Apply  heat  to  the  flask. 
The  salt  melts  and  gives  off  nitrous  oxide,  which 
being  heavier  than  air  collects  in  the  beaker. 
Note  that  combustion  is  supported  by  it  more 
actively  than  by  air,  using  paper  as  before. 


EXPERIMENTAL    CHEMISTRY. 


411 


The  equation  of  its  preparation  is  given  on  page 
187 

For  use  in  dentistry  it  is  liquefied  by  pressure  of  about 
50  atmospheres  and  the  liquefied  compound  sold  in 
wrought-iron  cylinders. 

III.  Nitrogen  Dioxide,  N^O,  or  NO. 

Formed  when  nitric  acid  acts  on  metals  as  the 
copper  cent  of  a  previous  experiment.  Collect- 
ing the  gas  by  displacement  with  water,  it  is 
colorless  (after  the  air  has  been  driven  off)  but 
% 


Fig.  43- 


Fig."  45- 


Fig.  44. 


in  presence  of  air  unites  directly  with  the  oxygen 
of  the  air  forming  N204=2(N02)  nitrogen  tetrox- 
ide,  which  has  deep-red  color  and  is  poisonous. 
Evaporate  to  dryness  the  blue  solution,  and  note 
that  it  is  a  crystalline  solid,  cupric  nitrate,  formed 
according  to  the  equation 

3Cu+8HN03=3Cu(N03)3+NA+4H,0 


412  DENTAL   CHEMISTRY. 

IV.  Nitric  Acid. 

Place  in  a  retort  (fig.  43)  of  about  250  c.c. 
capacity,  50  grammes  of  nitre  (potassium  nitrate) 
and  the  same  weight  nearly  of  sulphuric  acid. 
Fix  the  retort  by  a  clamp  on  the  ring  of  a  ring- 
stand  (fig.  44)  resting  it  on  wire  gauze,  the  mouth 
being  inclosed  by  a  wide-mouthed  flask  (re- 
ceiver), (fig.  45)  kept  cool  by  surrounding  with 
ice.  Nitric  acid  is  evolved  and  distils  over 
into  the  receiver.  Test  it  by  its  action  on  cop- 
per as  before. 

The  equation  has  been  already  given  on  page 
189. 

Nitric  acid  and  the  nitrates  are  strong  oxidizing  agents: 

place  in  a  test-tube  a  small  piece  of  tin  foil,   and  add   a 

little  nitric  acid;  energetic  action  takes  place,  the   tin  is 

oxidized,  and  the  nitric  acid   reduced,   according   to   the 

equation 

2HN03+Sn+H20  =  Sn(HO)4+N203 

The  action  of  nitric  acid  on  metals  as  a  rule  is  two-fold: 
first  the  metal  is  oxidized  and  second  the  oxide  or  hydrox- 
ide formed  is  dissolved  in  the  excess  of  acid,  forming  in 
turn  a  nitrate  and  water,  but,  in  the  action  of  nitric  acid 
on  tin,  the  oxygen  compounds  formed  are  both  insoluble 
in  excess  of  acid,  hence  nitrate  of  tin  is  not  formed.  In 
the  action  on  copper,  however,  we  have  first 

3Cu+2HN03+2H20=3Cu(HO)2+2NO 
second 

3Cu(HO)2+6HN03  =  3Cu(N03)2+6H20 
the  whole  action  being  represented  by  the  one   equation 
already  given  above. 

Tests  for  nitric  acid  will  be  given  in  the  chapter  on 
Analytical  Chemistry. 


EXPERIMENTAL    CHEMISTRY.  413 

Exercise  30.  Carbon:— 

A.  Heat  starch  or  sugar  on  platinum  foil.  A 
blackened  residue  is  obtained  resembling  char- 
coal. 

B.  Treat  sugar  with  sulphuric  acid  in  a  dish. 
A  similar  substance  is  obtained. 

C.  Heat  a  piece  of  a  match  or  tooth-pick  to 
redness  in  an  ignition  tube;  charcoal  will  be  left 
in  the  tube,  and  the  vapors  given  off  will  burn 
at  the  mouth  of  the  tube. 

D.  Heat  a  piece  of  bone  in  the  same  way, 
noting  offensive  odor. 

These  experiments  show  that  organic  substances  con- 
tain carbon,  and  blacken  when  heated,  if  non-volatile. 

E.  Obtain  some  solution  of  sulphuretted 
hydrogen,  used  in  the  laboratory  as  reagent,  and 
add  two  drops  of  it  to  half  a  test-tube  full  of 
water.  Note  the  odor  of  rotten  eggs.  Now 
weigh  out,  say,  five  grammes  of  powdered  char- 
coal, pour  it  into  the  tube,  cork  and  shake.  Let 
stand  fifteen  minutes  to  half  an  hour,  and  note 
that  the  odor  has  disappeared. 

This  experiment  shows  how  charcoal  (carbon)  absorbs 
gases  and  hence  acts  as  a  deodorizer. 

Exercise  31.  Carbon  monoxide: — 

A.  Prepare  this  gas  by  treating  10  grammes  of 
oxalic  acid  with  55  grammes  of  concentrated 
sulphuric  acid  in  a  flask,  connected  with  two 
Woulffs  flasks  (fig.  46)  containing  solutions 
of  caustic  soda.    Set  the  original  flask  on  asbes- 


414  DENTAL    CHEMISTRY, 

tos  and  heat  gently.  Collect  gas  given  off  over 
water.  Note  that  it  is  combustible  and,  that  if 
passed  over  heated  copper  oxide  in  an  ignition 
tube,  will  reduce  it. 

The  equation  of  its  production  is  as 
follows: — 

H,CA*+H,SO,=H,SO,.H,0 
+CO,+CO 

Most  of  the  illuminating  gas  now  used  is 
essentially  carbon    monoxide,    made    on  a 
Fig.  46.  large    scale  by  decomposing  steam  by  red 

hot  coal  thus: — 

H20+C  =  Ho+CO 
Mixed  with  hydrocarbons  it  is  used  for  illuminating  pur- 
poses.    Since  carbon  monoxide  is  poisonous,  deaths  from 
"blowing  out  the  gas"  are  thus  explained. 

Exercise  32.    Carbon  Dioxide:— 

A.  Prepare  this  substance  by  use  of  the  same 
apparatus  as  that  for  generating  hydrogen.  Place 
about  20  grammes  of  marble  dustf  in  the  flask, 
cover  well  with  water,  insert  cork  and  tubes, 
allow  delivery  tube  to  dip  to  the  bottom  of  a 
tumbler  through  a  card  covering  the  top,  and  add 
about  5  c.c.  of  hydrochloric  acid.  Carbon  diox- 
ide is  evolved,  and  being  heavier  than  air  collects 
at  the  bottom  of  the  tumbler.  The  equation  is 
asfollows:-CaC03+2HCl=CaCl3+H,0+CO, 

B.  Into  the  gas  collected  as  above  introduce 


*Oxalic  acid  or  hydric  oxalate. 
tCalcium  carbonate. 


EXPERIMENTAL    CHEMISTRY.  415 

a  lighted  taper.  The  flame  is  extinguished, 
showing  that  carbon  dioxide  does  not  support 
combustion. 

C.  Note  the  weight  of  the  gas  (high  specific 
gravity  with  reference  to  air)  by  pouring  quickly 
from  one  tumbler  to  another,  and  testing  the 
second  with  the  taper  as  above. 

D.  Shake  up  lime-water  with  the  gas  in  one 
of  the  tumblers,  and  note  that  it  becomes  turbid 
from  formation  of  calcium  carbonate,  according 
to  the  equation: — 

Ca  ( H  O )  ,+C03=CaC03+  H,0 
B.  Blow  air  exhaled  from  the  lungs  through 
a  glass  tube  into  lime  water,  and  notice  that  the 
same  thing  happens,  showing  that  the  breath 
contains  carbon  dioxide. 

F.  Remove  the  end  of  the  delivery  tube  from 
the  tumbler,  and  let  it  bubble  through  a  solu- 
tion of  litmus.  A  red  color  is  produced,  showing 
that  carbon  dioxide  has  an  acid  reaction,  hence 
was  formerly  called  carbonic  acid  gas. 

F.  Mix  2  or  3  grammes  of  powdered  copper 
oxide,  CuO,  with  about  a  quarter  of  a  gramme  of 
powdered  charcoal,  heat  in  an  ignition  tube  pro- 
vided with  perforated  cork  stopper  and  bent  tube 
passing  into  lime  water.  Carbon  dioxide  is 
evolved,  shown  by  the  turbidity  in  the  lime 
water;  the  copper  oxide  is  reduced  to  metallic 
copper,  shown  by  action  of  nitric  acid  on  residue. 
The  equation  has  already  been  given. 


41G  DENTAL    CHEMISTRY. 

Exercise  33.  Sulphur:— 

A.  Heat  a  small  piece  of  sulphur  in  an  ignition 
tube,  and  notice  the  suWimation  after  melting. 

The  sublimate  is  flowers  of  sulphur  (sublimed 
sulphur).  Pour  the  melted  sulphur  into  water 
and  let  cool.  Plastic  sulphur,  a  brownish,  elastic 
substance  is  formed. 

B.  Treat  dilute  ammonium  salphide  with  a 
few  drops  of  any  acid. 

Precipitated  sulphur  is  formed  which  is  more 
finely  divided  than  sublimed  sulphur  and  almost 
white  in  color.  The  pharmaceutical  preparation 
is  made  by  boiling  calcium  hydroxide  with  sul- 
phur and  water,  and  precipitating  with  HCl. 

C.  Boil  a  mixture  of  flowers  of  sulphur  and 
water  with  some  bright  silver  foil  and  note  that 
the  latter  is  tarnished,  according  to  the  equation 

2Ag+S=Ag.S 
silver  sulphide  being  formed.      Compare  with 
so-called  "oxidized  silver"  jewelry. 

Exercise  34.  Sulphurous  oxide:— 

A.  Prepare  by  acting  on  8  or  10  pieces  of 
sheet  copper,  1  to  2  inches  long  and  half  an  inch 
wide,  in  a  500  c.c.  flask  with  15  to  20  c.c.  con- 
centrated sulphuric  acid.  Arrange  as  if  for  mak- 
ing oxygen.  Heat.  As  soon  as  the  gas  is  given 
off,  regulate  evolution  by  lowering  flame.  Col- 
lect the  gas  and  also  pass  it  into  water.  The 
solution  is  called  sulphurous  acid,  and  will  bleach 


EXPERIMENTAL    CHEMISTRY.  417 

solution  of  logwood.  ( Use  a  drop  or  two  of  weak, 
alkaline  solution  of  logwood).  The  equation  is 
as  follows: — 

Cu+H,SO,=Cu(HO),+SO, 

and 
Cu(H0),+H3S0,=CuS0,+2H30 

B.  Show  by  use  of  taper  that  the  gas  does 
not  support  combustion,  nor  is  combustible. 

C.  Show  its  reducing  action  by  adding  solution 
of  permanganate  of  potassium  to  a  solution  of 
the  gas  in  water,  and  noticing  that  the  purple 
color  of  the  permanganate  is  destroyed  as  fast  as 
added. 

Exercise  35.  Sulphuric  acid: — 

A.  On  a  very  large  scale  sulphuric  acid  is  manufactured 
by  passing  into  large  leaden  chambers  simultaneously, 
the  vapors  of  sulphur  dioxide,  S02,(obtained  by  burning 
sulphur  or  pyrites  in  air)  nitric  acid,  and  steam,  a  supply 
of  atmospheric  air  also  being  provided  for.  The  follow- 
ing are  equations: — 

2S024-H20+2HN03=2H2S04+N203. 
The  nitrogen  trioxide,  NgOg,  next  takes  up  sulphur  diox- 
ide, SO2,  water,  and  oxygen  forming  what   is  known  as 
nitrosyl-sulphuric  acid,  as  follows: — 

2S02+N203+20+H20  =  2(S02.0H.N02). 

Steam  decomposes  this  substance  as  follows: — 
2(SO2.OH.NO0+H2O  =  2H.SO,+N2O3. 
The  nitrogen  trioxide  again  forms  nitrosyl-sulphuric  acid, 
and  the  process  thus  goes  on  indefinitely  though  it  is  nec- 
essary to  add  small  portions  of  nitric  acid  daily,  since 
there  is  unavoidable  loss  of  small  portions  of  it  or  of  the 
oxides  of  nitrogen  in  the  process. 


418  DENTAL    CHEMISTRY. 

The  oxides  of  nitrogen  serve  as  agents  in  this  process 
for  the  transfer  of  atmospheric  oxygen,  only  a  portion  of 
the  oxygen  necessary  being  derived  from  the  nitric  acid 
directly. 

The  manufacture  of  sulphuric  acid  may  be  illustrated 
in  the  laboratory  by  means  of  an  apparatus  consisting  of 
a  large  balloon  flask  (fig.  47)  fitted  with  a  stopper  having 


Fig.  47. 

five  openings,  and  connected  by  tubes  with  three  small 
flasks  or  retorts,  from  which  are  supplied  steam,  sulphur 
dioxide,  and  oxides  of  nitrogen.  Air  is  supplied  by  a 
bellows. 

B.  Add  one  c.c.  of  sulphuric  acid  to  1,000  c.c. 
of  water  and  note  that  it  still  reddens  litmus. 
This  experiment  shows  the  strongly  acid  char- 
acter of  sulphuric  acid. 

C.  Place  in  a  test-tube  a  few  drops  of  sulphuric 
acid,  and  add  the  same  amount  of  water.  Hold 
the  tube  at  the  bottom,  and  note  development 
of  heat.  This  experiment  shows  the  strong 
affinity  of  sulphuric  acid  for  water,  and  the  danger 


EXPERIMENTAL    CHEMISTRY.  419 

which  attends  careless  mixing  of  it  with  water. 

D.  Go  back  now  to  experiment  30.B.,  and 
explain  the  carbonizing  of  the  sugar  by  the 
abstraction  of  water  from  it  on  part  of  the  sul- 
phuric acid,  bearing  in  mind  that  sugar  is  com- 
posed of  hydrogen  and  oxygen,  in  proportion  to 
form  water,  plus  carbon. 

E.  Note  the  heavy,  oily  character  of  the  acid 
and  thus  account  in  part  for  the  name  "oil  of 
vitriol." 

F.  Note  the  action  of  this  acid  on  various  met- 
als as  tin,  copper,  iron,  zinc.  Dilute  with  water 
say  about  one-third  and  note  action.  (See 
page  159) 

G.  Note  the  action  of  sulphuric  acid  on  hemp 
paper,  reducing  it  to  pyroxylin,  (see  page  159) 

H.  Put  a  small,  thin  piece  of  bone  into  a  dish 
and  act  on  it  with  sulphuric  acid,  noticing  that 
it  is  dissolved.    (See  page  1 59). 
Exercise  36.    Hydric  siilpliide,  H^S:— 

On  account  of  the  fetid  odor  of  this  gas  there  should 
be  in  every  laboratory  special  apparatus  for  its  preparation. 
The  apparatus  often  employed  is  that  of  Kipp  (fig.  48), 
by  use  of  which  the  disagreeable  odor  is  avoided. 

A.  Make  sulphuretted  hydrogen  by  placing 
about  20  grammes  of  ferrous  sulphide  in  small 
lumps^  in  a  flask  (provided  with  twice  perfora- 
ted cork,  thistle  tube,  and  delivery  tube,  the  latter 
passing  into  water)   covering  with  water,  and 

*The  powdered  sulphide  slowlv  changes  on  exposure  to  air.    Hard  lumps  should 
be  procured. 


420  DENTAL    CHEMISTRY 

pouring  into  the  thistle  tube  sulphuric  acid  in 
small  quantities  at  a  time  until  brisk  efferves- 
cence takes  place.  When  the  evolution  of  the 
gas  becomes  slow,  add  a  little  more  acid.  More 
exactly  dilute  the  acid  in  the 
start  with  six  times  its  volume 
of  water  and  pour  upon  the  dry 
ferrous  sulphide,  adding  more 
acid  as  evolution  of  gas  becomes 
slow.  Too  much  acid  forms  a 
sulphate  and  retards  action. 

Hydrochloric  acid  may  be  used 
instead  of  sulphuric,  in  which 
case  1 0  or  1 2  grammes  of  ferrous 
sulphide  will  need  2  or  3  tea- 
spoonfuls  of  strong  hydrochloric 
Fig"^.  acid  to   begin   with,    and    more 

after  the  disengagement  of  gas  slackens.    The 
equations  are  as  follows: — 

FeS+H,S0,=H3S+FeS0, 
and 
FeS-f(HCl),=H,S+FeCU 

B.  Note  that  when  washed  in  a  little  water, 
it  is  dissolved  in  part  in  the  latter,  the  solution 
turning  blue  litmus  paper  slightly  red. 

C.  Note  that  the  gas  is  combustible,  burn- 
ing with  a  blue  flame.  Hold  a  cold  plate  to 
the  flame  and  note  deposition  of  sulphur  on  it. 

D.  Make  a  solution  of  the  gas  in  water,  pour 
into  a  tube  and  let  stand  uncorked  a  few  davsL 


EXPERIMENTAL    CHEMISTRY.  421 

Note  that  the  solution  becomes  muddy,  depos- 
its sulphur,  and  loses  its  odor,  according  to 
the  equation. 

2H3S)+03=2H30+S,. 

E.  Pass  some  of  the  gas  into  ammonia  water 
and  note  the  change  in  color  to  yellow  and  the 
disgusting  odor,  according  to  the  equation 

2NH3+H.S-(NHJ.S 

F.  Drop  a  drop  of  the  solution  of  the  gas  on 
a  piece  of  metal,  and  notice  the  blackening  that 
occurs,  from  formation  of  metallic  sulphides. 
Thus  in  case  of  silver 

2Ag+H,S-Ag,§+H, 

G.  Expose  an  amalgam  plug  to  the  action  of 
the  gas  or  solution  of  it,  and  also  to  the  act- 
ion of  decaying  food,  such  as  would  be  found 
in  the  mouth,  and  notice  the  blackening. 

Exercise  37.  Carbon  disulphide,  CS^. 

A.  Note  the  disgusting  odor,  and  colorless, 
volatile,  highly  refractive  character  of  this  sub- 
stance. 

B.  Note  that  it  is  almost  insoluble  in  water, 
but  soluble  in  alcohol.  Note  that  it  dissolves 
sulphur,  iodine,  phosphorus,*  some  of  the  alka- 
loids, also  volatile  and  fixed  oils.  Perform  this 
experiment  according  to  the  time  at  your  dis- 
posal. 

C.  Note  that  carbon  disulphide  is  inflammable. 

♦See  next  experiment. 


422  DENTAL    CHEMISTRY. 

*    Exercise  38.  Phosphorus*:— 

A.  Place  a  small  fragment  of  phosphorus  carefully  on 
a  dish,  and  allow  it  to  remain  thus  exposed  to  the  air. 
It  first  becomes  hot  from  oxidation,  then  takes  fire.  This 
experiment  shows  that  phosphorus  combines  with  oxy- 
gen at  ordinary  temperatures,  hence  must  be  kept  under 
water.  Note  the  garlic-like  odor  of  the  fumes  and  the 
whitish  vapors  given  off.  Take  another  small  piece  on  a 
dish  into  a  dark  closet,  and  note  that  the  vapors  are  lum- 
inous. 

B.  Using  very  small  pieces  and  working  rapidly  note 
that  phosphorus  is  but  little  soluble  in  alcohol,  but  is 
very  soluble  in  chloroform,  and  carbon  disulphide. 

C.  Pour  the  solution  of  phosphorus  in  carbon  disulphide 
on  filter  paper,  and  let  dry.  Note  that  as  soon  as  the 
carbon  disulphide  has  evaporated,  the  phosphorus  takes 
fire. 

D.  Combine  phosphorus  and  iodine  directly,  by  bring- 
ing together  in  a  dish  a  little  of  each.  Note  the  light 
and  heat  accompanying  the  action. 

E.  Seal  up  in  an  ignition  tube  a  few  pieces  of  phosphor- 
us and  heat  the  tube  gradually  to  300°  C.  Notice  that 
it  is  gradually  converted  to  a  red  powder.  Open  the  tube 
and  notice  that  this  form  of  phosphorus  does  not  take 
fire  as  readily  as  ordinary  phosphorus,  and  is  not  as  sol- 
uble in  carbon  disulphide. 

Exercise  39.  Phosphoric  acid. 

A.  Dry  a  small  piece  of  phosphorus  quickly 
between  folds  of  filter  paper,  place  it  in  a 
small,  porcelain  dish,  which  is  set  on  a  glass 
plate.    Touch    the     phosphorus    with     heated 

♦Inexperienced  persons  should  not  attempt  this  exercise. 


EXPERIMENTAL    CHEMISTRY.  423 

wire.     It  is  at  once  inflamed.    Cover   over  tlie 

dish  with  a  bell  jar  (fig.  49).     Note  that    the 

white    vapors    of  phosphoric    oxide 

condense  into  flakes,  and  fall  on  the 

glass  plate.    Dissolve  the  flakes  in  a 

few  c.c.  of  water,  using  a  glass  rod  to 

collect  them.     The  solution   has  an 

acid  reaction,  and  is  meta-phosphoric 

Fig  49        acid*,  HPO3  according  to  the  equation 

P,+(0.)5=2(P30s) 

and 

PA+H,0=2HP03 

B.  To  a  little  of  the  solution  of  meta-phosphoric 
acid  thus  formed  add  solution  of  white  of  egg. 
The  latter  is  coagulated. 

C.  Evaporate  the  solution  of  meta-phosphoric 
acid  formed  in  experiment  A  and  notice  that  it 
becomes  syntpy. 

D.  Take  some  of  the  syrupy  acid,  dilute  with 
a  little  water,  and  add  solution  of  white-of-egg. 
The  latter  is  not  coagulated.  The  liquid  has  been 
converted  into  ortho-phosphoric  acid. 

These  experiments  show  that,  if  phosphorus 
is  burned  in  air,  phosphoric  oxide  is  formed  which, 
uniting  with  water,  forms  meta-phosphoric  acid, 
which  in  turn  is  converted  into  ortho-phosphoric 
acid  on  boiling.  Read  carefully  the  sections  on 
phosphoric  acid  pages  183  to  187. 


*Called  glacial  phosphoric  acid. 


424 


DENTAL    CHEMISTRY, 


Exercise  40.  Chlorine:— 

A.  Prepare  chlorine  by  heating  black  oxide  of 
manganese  with  hydrochloric  acid  (fig.  50). 
Weigh  out  about  50  grammes  of  manganese  diox- 
ide. Cover  with  hydrochloric  acid,  and  shake  well. 

Heat  and  collect  gas  in  dry 
bottles  by  downward  dis- 
placement. Note  the  yellow- 
ish-green color  and  extremely 
penetrating,  suffocating  odor, 
producing  violent  coughing 
and  inflammation,  so  that  it 
should  be  made  either  in  a 
fume  chamber  or  where  there 
is  a  strong  current  of  air. 
Several  bottles  may  be  filled 
with  the  gas. 
The  equation  of  its  formation  is  as  follows: — 
Mn03+4HCl=MnCl.+  2H,0+Cl, 

The  method  depends  on  the  oxidation  of  the  hydro- 
gen of  hydrochloric  acid  by  the  oxygen  in  the  manganese 
dioxide.  Fig.  51  shows  an  apparatus  for  making  chlorine 
water,  ammonia  or  hydrochloric  acid,  provision  being 
made  for  washing  the  gases  by  means  of  Woulff's  bottles. 

B.  Collect  the  gas  in  water  noticing  that  it  is 
soluble,  forming  a  greenish-yellow  liquid.  The 
solution  has  bleaching  properties  shown  by  pour- 
ing it  on  colored  flowers. 

C.  Fill  a  test-tube,  half  with  chlorine  gas  and 
half  with  hydrogen.    Wrap  the  tube  in  cloth  and 


Fig.  50 


EXPERIMENTAL    CHEMISTRY.  425 

bring  it  close  to  a  naked  flame.  Combustion 
rapidly  takes  place  and  with  explosive  violence, 
the  two  gases  uniting. 

H3+C1,=2HC1 

This  experiment  shows  the  intense  affmity  of 
chlorine  for  hydrogen.  Its  affmity  for  other  ele- 
ments is  also  great,  and  may  be  illustrated  by 
the  following  experiments. 

Experiment  C.  quantitatively  performed  re- 
quires the  apparatus  of  fig.  54. 

D.  Powder  antimony  and  drop  some  of  the 
finely  powdered  metal  into  a  bottle  of  chlorine. 
Note  that  each  particle  of  metal  burns  while 
passing  through  the  gas,  forming  a  white  sub- 
stance. 

Sb+3Cl=SbCl3 

E.  Paper  moistened  with  warm  oil  of  turpentine 
dropped  into  a  bottle  containing  chlorine  inflames, 
owing  to  the  intense  affmity  of  the  chlorine  for 
the  hydrogen,  evolving  so  much  heat  that  the 
whole  takes  fire,  dense  clouds  of  smoke  being 
formed. 

F.  Fill  a  test-tube  full  of  water,  and  add  one 
drop  of  solution  of  hydric  sulphide.  Pour  in 
some  chlorine  water,  and  notice  that  the  odor  of 
the  sulphuretted  hydrogen  is  destroyed. 

The  equation  is 

H,S+2C1=2HC1+S 

Chlorine  acts  as  a  deodorizer  and  disinfectant  by  com- 


426 


DENTAL    CHEMISTRY. 


bining  directly  with  hydrogen  or  by  decomposing  water 
with  liberation  of  oxygen,  which,  when  nascent,  has  strong 
tendency  to  oxidize  other  substances. 

Exercise  41.  Hydrochloric  acid:— 

A.  Prepare  the  gas  by  use  of  an  apparatus 
(fig.  50  or  51)  similar  to  that  in  which  ammonia 


Fig.  51. 

is  generated  but  provided  with  a  funnel  tube. 
Place  in  the  flask  about  20  grammes  of  sodium 
chloride,  add  about  30  c.c.  of  concentrated  sul- 
phuric acid,  mix  well,  heat,  and  pass  into  water. 
Note  that  the  gas  is  colorless,  very  irritating  to 
the  air  passages,  and  that  it  reddens  litmus.  The 
equation  has  been  already  given. 

B.  Note  the  white  clouds  which  arise  from 
the  solution  in  water,  due  to  the  affinity  which 
the  acid  has  for  the  aqueous  vapor  in  the  air,  the 
clouds  being  formed  of  minute  particles  of  hydro- 


EXPERIMENTAL    CHEMISTRY.  427 

chloric  acid.  The  solution  in  water  is  known  to 
commerce  as  hydrochloric  or  muriatic  acid,  but 
the  acid  itself  is  a  gaseous  body. 

C.  Reconsider  29  B.  Note  equation  at  end. 

Exercise  42.  Bromine. 

A.  Put  a  very  little  black  oxide  of  manganese, 
a  small  crystal  of  bromide  of  sodium,  half  a  c.c. 
of  water,  and  ten  drops  of  sulphuric  acid  into  a 
test-tube.  Warm  gently,  and  note  red  fumes  of 
bromine  given  off,  with  odor  resembling  chlor- 
ine:— 

MnO,+2NaBr+2H,SO,= 

MnSO,+Na,SO,+Br,+2H30 

B.  To  1 0  c.c.  of  a  solution  of  1 00  grammes  sod- 
ium hydrate  in  200  c.c.  of  water  add  1  c.c.  of 
bromine,  taking  it  up  out  of  a  bottle  by  means  of 
a  nipple  pipette,    (fig.   53)   graduated  to  1    c.c. 

Note  that  the  bromine  unites  with   the 
sodium  hydrate  and  that  heat  is  given  off. 
Sodium  hypobroniite  is  formed: — 
2NaHO+Br,=NaBrO+NaBr+H,0 
Exercise  43.  Iodine:— 
A.  Prepare  iodine  by  mixing  2  grammes 
of  potassium  iodide,  4  grammes  of  black 
Fig.  53.  oxide  of  manganese,  and  a  little  sulphuric 
acid  in  a  flask  of  1  or  2  liters  capacity.  Heat  gently 
in  a  sand-bath,  and  note  that  the  vessel  will 
gradually  be  filled  with  the  heavy  violet  vapor 
of  iodine,  which  will   condense    in   the     upper 


428  DENTAL    CHEMISTRY. 

parts  of  the  flask  in  the  form  of  grayish-black 
scales: — 

2KI+MnO,    2,S0  = 
K.S0,+MnS0,+2H,0+I,. 

B.  Note  that  iodine  is  but  sparingly  soluble 
in  water,  but  soluble  in  alcohol,  and  in  an  aque- 
ous solution  of  potassium  iodide. 

C.  Note  that  iodine  is  soluble  in  carbon  disul- 
phide,  and  in  chloroform,  and  that  the  color  of 
the  solutions  is  violet,  cause  not  known. 

D.  Cut  a  slice  from  a  potato  and  drop  a  drop 
of  tincture  of  iodine  (solution  in  alcohol)  upon  it. 
A  blue  color  is  formed,  due  to  the  reaction  of 
iodine  and  the  starch  in  the  potato. 

E.  To  a  solution  of  potassium  iodide  add  car- 
bon disulphide  and  shake  well.  No  change  in 
the  color  of  the  disulphide  takes  place. 

Now  add  a  drop  of  chlorine  water,  and  shake 
again,  and  note  that  the  carbon  disulphide  is 
colored  violet  by  iodine,  set  free  from  potassium 
iodide  by  action  of  the  chlorine  water: — 
2KI+a=2KCl+I, 
Exercise  44.  Hydrofluoric  acid:— 
Heat  a  glass  plate  slightly  and  cover  it  with  a 
thin  layer  of  wax.     Let  cool,  and  scratch  some 
figures  through  the  wax,  thus  exposing  the  glass. 
Set  the  plate  in  the  open  air  over  a  dish  of  lead 
in  which  sulphuric  acid  is  mixed  with   equal 
weight  of  powdered  fluor  spar: — 

CaF,+H3SO,=2HF+CaSO, 


EXPERIMENTAL    CHEMISTRY.  429 

On  removing  the  wax  the  glass  will  be  found  to 
be  etched  wherever  its  surface  was  exposed  to 
the  vapors  of  the  acid.  This  experiment  illus- 
trates the  action  of  hydrofluoric  acid  on  silica  in 
glass  converting  it  into  either  a  fluoride  of  silicon 
or  into  hydrofluosilicic  acid. 

Exercise  45.  Potassium. 

Drop  a  small  piece  of  potassium  into  a  dish 
containing  water.  Combustion  takes  place,  and 
the  flame  is  of  a  molet  color,  the  former  due  to 
the  setting  free  of  the  hydrogen  of  the  water, 
the  latter  to  the  vapor  of  the  potassium.  The 
equation  is  as  follows: — 

K+H30=K0H+H 
The  liquid  has  now  a  soapy  feel,  and  turns  red 
litmus  blue. 

Exercise  46.  Sodium. 

Repeat  experiment  45,  using  sodium  instead  of 
potassium.  Note  that  there  is  less  vigorous  act- 
ion and  no  flame,  unless  the  metal  is  in  contact 
with  the  glass  when  the  characteristic  yellow 
flame  of  sodium  may  be  seen.  The  liquid  be- 
comes alkaline  as  before. 

Exercise  47.  Compounds  of  potassium 
and  sodium. 

A.  Make  a  solution  of  potassium  hydroxide  in 
water  in  strength  about  1  in  8,  and  add  to  it  iodine 
scales  until  the  brown  color  no  longer  disappears. 
Potassium  iodide  is  formed  according  to  the  equa- 
tion 


430  DENTAL    CHEMISTRY. 

6KHO+l6=5KI+Kn03+3H30 

The  resulting  solution  contains  potassium  iodide  mixed 
with  the  iodate.  The  iodide  may  be  separated  by  evap- 
oration, deflagration  with  about  lo  per  cent,  powdered 
charcoal,  solution  in  hot  water,  and  crystallization. 

B.  Heat  excess  of  sodium  sulphate  with  water 
at  a  temperature  of  about  33°C(91.4°  F.). 
Filter  the  solution  into  small  bottles  and  then 
cork.  Remove  the  corks  and  shake  well,  when 
the  salt  will  suddenly  crystallize  out. 

C.  In  connection  with  sodium  and  potassium 
it  is  customary  to  consider  compounds  of  the 
radical  ammonium.  For  the  present  it  will 
suffice  to  note  the  volatile  character  of  compounds 
of  this  radical.  Heat  any  one  of  them,  as  ammon- 
ium chloride,  on  foil  and  notice  that  it  is  volatil- 
ized at  low  red  heat. 

Exercise  48.  Magnesium. 

A.  Take  up  with  the  tongs  a  piece  of  mag- 
nesium four  or  five  inches  long,  and  hold  in  the 
Bunsen  flame,  it  burns  rapidly,  and  white  mag- 
nesium oxide  is  formed,  according  to  the  equation 

Mg+0.=MgO. 

B.  Dissolve  magnesium  sulphate  in  hot  water, 
and  add  a  concentrated  solution  of  sodium  car- 
bonate. Notice  the  white  precipitate.  Keep  on 
adding  the  solution  of  sodium  carbonate  until  no 
more  precipitate  is  formed.  Collect  the  precipi- 
tate on  a  filter,  and  dry  at  a  low  temperature. 
What  is  known  as  magnesia  alba  or  light  magnesia 


EXPERIMENTAL    CHEMISTRY.  431 

is  obtained  (MgC03),.Mg(HO),.5H,0,  according  to 
tlie  equation 

5MgS04+5Na,C03+6H30= 
(MgC03),IVlg(HO)..5H.O+5Na.SO,+CO. 
Heavy  magnesia  is  the  name  given  to  mag- 
nesium carbonate,  when  the  precipitate  obtained 
as  above  is  separated  by  evaporation  to  dryness 
and  washing  out  of  the  sodium  sulphate. 
Experiment  49.  Calcium. 

A.  Make  what  is  known  as  lime-water  by 
adding  1  gramme  of  calcium  oxide  to  30  c.c.  of 
distilled  water,  allowing  the  lime  to  slake  and 
shaking  occasionally  for  half  an  hour.  Let 
settle,  decant,  and  then  add  300  c.c.  of  distilled 
water,  place  in  a  well-stoppered  bottle,  shake 
occasionally,  and  pour  off  for  use. 

B.  Weigh  out  about  10  grammes  of  marble 
dust  (calcium  carbonate)  in  small  pieces,  place 
them  in  a  dish,  and  add  hydrochloric  acid  as  long 
as  any  effervescence  takes  place.  The  equation 
is  as  follows: — 

CaC03+2HCl=CaCl.+CO,+2H,0 
Filter,  and  obtain  in  the  filtrate  solution  of  cal- 
cium chloride.    Now  mix  this  solution  with  one 
of  sodium  carbonate,  and  obtain  a  white  precipi- 
tate, according  to  the  equation 

CaCl3+Na.C03=2NaCl+CaC03 
Note  that  the  precipitate  is  a    carbonate   by  col- 
lecting on  filter,    washing,    drying,  and  adding 
hydrochloric  acid,  which  produces  effervescence. 


432  DENTAL    CHEMISTRY, 

and  the  gas  given  off,  if    passed  through  lime- 
water,  makes  it  turbid. 

The  above  experiment  illustrates  the  mode  of  pre- 
paration of  precipitated  calcium  carbonate.  It  also  illus- 
trates double  decomposition.  To  form  an  insoluble 
substance  by  double  decomposition  we  must  remember 
that  the  substances  put  together  should  be  soluble.  One 
should  contain  the  metal  of  the  insoluble  compound 
required,  and  the  other  the  acid  radical  of  the  same  com- 
pound. Further,  the  decomposition  must  not  result  in 
the  formation  of  any  substance  capable  of  holding  in 
solution  the  substance  which  we  wish  to  form,  else  no 
change  will  occur.  In  this  case  we  wish  to  show  the 
formation  of  calcium  carbonate.  Now  the  metal  of  calcium 
carbonate  is  calcium,  hence  we  must  take  a  soluble  com- 
pound of  calcium.  (See  Rules  for  Solubility  page  (70).  The 
acid  radical  of  calcium  carbonate  is  found  in  all  carbonates, 
and  hence  we  must  take  a  soluble  carbonate.  This  reduces 
us  to  a  choice  of  two  of  a  few  compounds.  Thus  we 
have: — 

Soluble  salts  of  Calcium.  Soluble  Carbonates, 

Calcic  Chloride.  Hydric  Carbonate. 

"       Bromide.  Potassic         " 

Iodide.  Sodic  " 

"       Hydrate.  Ammonic       " 

etc. 
Any  of  these  combinations  may  be  used  except  that  with 
hydric  carbonate,  which  will  form  an  acid  (hydrochloric), 
which  would  hold  the  calcic  carbonate  in  solution. 

Thus  CaCl2+H2C03=2HCl-f  CaCOj. 
But,  on  the  other  hand 

CaCl2+K,C03=2KCl+CaC03, 
and  so  on. 


EXPERIMENTAL    CHEMISTRY.  433 

Exercise  50.  Aluminium. 

A.  Procure  any  small  article  made  of  alum- 
inium and  compare  its  weight  with  that  of  an 
article  of  similar  size  of  tin,  lead,  iron,  and  plat- 
inum. 

B.  Place  a  small  piece  of  aluminium  in  each  of 
two  test-tubes.  To  one  add  hydrochloric  acid 
and  to  the  other  add  sodium  hydroxide.  Hydro- 
gen is  evolved  in  each  case,  and  the  chloride  of 
aluminium  and  aluminate  of  sodium  respectively 
formed.    The  equations  are 

AU+6HCl=Al,Cl6+3H, 
and 
Al+3NaHO=Na3A103+H3 

Exercise  51.  Iron:— 

A.  Test  the  solubility  of  iron  in  hydrochloric 
acid  by  acting  on  a  small  piece  of  iron  wire  with 
dilute  hydrochloric  acid.  Note  that  the  solution 
becomes  green  from  formation  of  ferrous  chloride, 
according  to  the  equation 

Fe+2HCl=FeCl3+H, 
Now  add  nitric  acid  and  note  that    the    solution 
becomes  yellow  from  formation  of  ferric  chloride. 

In  order  to  obtain  ferric  chloride  the  operation  should 
be  conducted  as  follows: — dissolve  by  aid  of  heat  i  gramme 
of  fine  iron  wire  in  about  4  c.c.  of  hydrochloric  acid  prev- 
iously diluted  with  2  c.c.  of  water.  Filter,  warm,  mix 
with  2  c.c.  more  of  hydrochloric  acid  and  add  slowly  and 
gradually  about  0.6c.c.  of  nitric  acid — The  equation  is 
6FeCl2+2HN03+6HCl  =  3FeoCl6+4H,0+2NO 


434  DENTAL    CHEMISTRY. 

"The  solution  as  above  is  evaporated  in  a  fume  chamber 
as  long  as  red  vapors  escape  and,  if  it  gives  a  blue  pre- 
cipitate with  potassium  ferricyanide,  it  is  to  be  heated  with 
a  few  drops  more  of  nitric  acid  till  it  does  not.  Then 
mix  with  4  c.c.  of  hot  water  and  set  aside,  when  it  forms  a 
solid  mass. 

B.  To  a  solution  of  ferric  chloride  in  a  test- 
tube  add  some  powdered  zinc,  and  note  that  the 
solution  becomes  nearly  colorless  owing  to  the 
reduction  of  the  ferric  chloride  to  ferrous,  accord- 
ing to  the  equation 

Fe,Cl6+Zn=2FeCl,+ZnCl, 

C.  Dissolve  iron  in  dilute  sulphuric  acid,  evap- 
orate, and  crystallize,  obtaining  gi^een  vitriol, 
ferrous  sulphate,  according  to  the  equation 

Fe+H,SO,=FeSO,+H, 

Exercise  52.  Manganese:— 

A.  Heat  in  a  porcelain  crucible  2  grammes  of 
the  black  oxide  of  manganese  with  2  grammes 
of  potassium  hydroxide  and  1  of  potassium  chlor- 
ate. 

The  fused  mass  turns  green.  Let  cool,  dis- 
solve in  distilled  water,  filter,  and  pass  carbon 
dioxide  into  the  filtrate.  It  turns  purple  from  con- 
version of  the  green  manganate  of  potassium  into 
the  purple  permanganate,  according  to  the  equa- 
tion 

3MnO,+6KHO+KC103=3K,MnO,+KCl+3H,0 
and 

3K,MnO,+2C03=K.Mn,08+MnO,+2K3C03 


EXPERIMENTAL    CHEMISTRY.  435 

Exercise  53.  Chromium: — 

Prepare  chromic  "acid,"  so-called,  chromic 
trioxide,  Cr03,  by  dissolving  a  few  grammes  of 
potassium  dichromate  in  water  and  adding  5  parts 
by  volume  of  strong  sulphuric  acid  to  4  parts  by 
volume  of  the  dichromate  solution.  Let  cool. 
Chromic  trioxide  separates  out  in  deep  red  crys- 
tals of  a  purplish  hue.  The  equation  is  as  fol- 
lows : — 

K,CrA+HaSO,=K,SO  +H,0+2Cr03 

Collect  the  crystals  on  asbestos,  wash  with  a 
little  nitric  acid,  and  dry  by  passing  a  current  of 
warm,  dry  air  through  a  tube  in  which  they  have 
been  placed. 

Chromic  trioxide  is  an  energetic  oxidizing  agent  and 
must  be  kept  away  from  glycerin,  alcohol,  sugar,  tannin, 
and  organic  substances  generally  with  which  it  forms 
explosive  compounds. 

Exercise  54.  Zinc. 

A.  The  solubility  of  zinc  in  various  acids, 
strong  and  dilute,  has  already  been  noticed. 

B.  Note  the  rapid  combustion  of  zinc  in  the 
Bunsen  flame  and  the  production  of  zinc  oxide 

Zn+0=ZnO. 

C.  Note  the  physical  change  in  zinc  oxide 
which  takes  place  when  the  latter  is  heated,  the 
color  becoming  yellow,  but  white  again  on  cool- 
ing. 

D.  Experiments  illustrating  the  reducing 
power  of  zinc  have  already  been  performed. 


430  DENTAL    CHEMISTRY 

Exercise  55.  Lead:— 

A.  Dissolve  a  little  of  the  acetate  or  nitrate  of 
lead  in  half  a  pint  of  water,  and  suspend  in  the 
centre  of  the  solution  a  piece  of  zinc.  Set  aside 
and  note  the  slow  formation  of  crystalline  met- 
allic lead  {^lead-tree)  on  the  zinc  while  the  zinc 
goes  into  solution. 

The  equation  is  as  follows: 

Pb(N03),+Zn=Zn(N03),+Pb. 
This  experiment  shows  the    expulsion  of  lead 
from  its  compounds  by  zinc,  and  illustrates  sub- 
stihition. 

B.  Melt  together  in  a  crucible  2  parts  by 
weight  of  lead,  1  of  antimony,  and  1  of  tin.  The 
alloy  is  called  type-metal. 

C.  Melt  together  1  part  lead  and  2  parts  tin. 
The  alloy  is  called  solder. 

Exercise  56.  Copper: — 

A.  Boil  1  part  by  weight  of  fme  copper  wire 
with  3  of  concentrated  sulphuric  acid.  Keep  up 
the  boiling  till  the  action  of  the  acid  on  the 
metal  ceases,  and  most  of  the  copper  is  dissolved. 
A  blue  solution  is  obtained.  Dilute  with  the  same 
amount  of  water  as  acid  used,  filter,  and  set  aside 
in  an  open  dish  in  a  cool  place  for  crystallization. 
Large,  transparent,  deep-blue  crystals  of  cupric 
sulphate  separate  out. 

B.  Note  that  hydrochloric  acid  and  sulphuric 
acids  when  diluted  do  not  attack  copper  appre- 
ciably, not  even  when  boiled,  but  that  if  copper 


EXPERIMENTAL    CHEMISTRY.  437 

foil  be  heated  in  the  air  till  tarnished  by  forma- 
tion of  copper  oxide,  the  dilute  acids,  on  applica- 
tion of  gentle  heat,  dissolve  the  oxide  and  thus 
clean  the  metal. 

C.  Dip  a  bright  steel  knife-blade  into  a  solu- 
tion of  cupric  sulphate,  and  note  that  the  steel 
expels  the  copper,  which  is  deposited  on  the 
blade: — 

CuSO,+Fe=FeSO,+Cu. 

Exercise  57.  Bismuth: — 

A.  Prepare  subnitrate  of  bismuth  by  dissolving 
with  aid  of  heat  about  1  gramme  of  the  metal  in 
2  c.c,  of  nitric  acid  diluted  with  1  c.c.  of  water. 
The  equation  is 

Bi+4HN03=Bi(N03) +N0+2H,0. 

Evaporate  the  solution  to  about  half  its  volume, 
so  as  to  expel  excess  of  acid,  and  pour  it  into 
large  excess  of  water,  say  100  c.c.  A  white 
precipitate  of  bismuth  oxynitrate  (subnitrate)  or 
bismuthyl  nitrate,  as  it  is  called,  is  formed  accord- 
ing to  the  equation 

Bi(N03)3+2H,0=BiON03.H,0+2HN03. 
Collect  precipitate  on  filter,  wash,  dry,  and  note 
weight  of  the  powder  and  its  solubility  in  acids. 

Exercise  58.  Silver: — 

Dissolve  a  dime  in  nitric  acid,  and  note  the 
blue  solution  obtained,  due  to  presence  of  nitrate 
of  copper  along  with  the  silver.     Dilute  with 


438 


DENTAL    CHEMISTRY. 


water,  and  add  excess  of  solution  of  common  salt. 
Note  the  precipitation  of  white  silver  chloride, 
according  to  the  equation 

AgN03+NaCI  AgCl+NaNOj. 
Filter,  and  add  water  to  the  precipitate,  using  the 
wash-bottle.  After  the  precipitate  has  been  well 
washed,  remove  the  filtrate  and  replace  the  flask 
containing  it  by  a  clean,  empty  flask.  Make  a 
small  hole  in  the  filter  paper,  and  wash  the  pre- 
cipitate through  into  the  flask,  by  means  of  the 
stream  from  the  wash  bottle.  After  it  has  set- 
tled, drain  off -the  supernatant  liquid,  and  let 
the  precipitate  dry.  When  dr>',  place  in  a  small 
porcelain  crucible  and  fuse  at  gentle  heat.  Let 
cool,  and  when  cold,  place  a  piece  of  sheet  zinc 
on  it,  cover  with  water,  to  which  a  few  drops  of 
sulphuric  acid  have  been  added,  and  set  aside  for 
a  day  or  two.  Spongy  silver  will  be  formed 
from  the  decomposition  of  the  silver  chloride  by 
the  zinc,  according  to  the  equation 
2AgCI +Zn=ZnCl,+Ag, 

B.  Drop  a  drop  of  a  solution  of  sulphuretted 
hydrogen  on  a  piece  of  silver,  and  note  that  it 
becomes  tarnished,  from  formation  of  silver  sul- 
phide. Wash  the  metal,  heat  it  to  redness,  and 
note  that  the  metal  is  again  bright,  the  silver 
sulphide  being  reduced  io  metallic  silver. 

C.  Note  that  hydrochloric  acid  and  dihite  sul- 
-phuric  acid  attack  silver  but  slightly.    Add  pot 


EXPERIMENTAL    CHEMISTRY.  439 

assium  permanganate  to  dilute  sulphuric  acid, 
drop  in  a  piece  of  silver,  and  notice  that  the 
metal  is  now  dissolved. 

Exercise  59.  Mercury. 

Into  a  solution  of  corrosive  sublimate  put  a 
piece  of  bright  copper  foil,  Heat  for  a  few 
moments.  Take  out  the  copper  and  notice  that 
it  is  covered  with  mercuiy.  (This  experiment 
also  illustrates  substitution,  according  to  the 
equation  HgCl2+Cu=CuCl2+Hg). 

B.  Dry  the  copper  treated  as  in  Ex.  52  be- 
tween folds  of  filter  paper.  Put  it  into  the  bot- 
tom of  a  narrow  glass  tube,  closed  at  one  end, 
and  heat  the  copper  to  redness.  The  mercury 
will  volatilize,  and  be  deposited  in  the  tube  in 
microscopic  globules.  Examine  with  low  power 
of  microscope:  the  globules  appear  round  and 
opaque  by  transmitted  light,  but  shine  like 
stars  by  reflected  light. 

C.  Insert  into  the  tube  containing  the  vola- 
tilized mercury  a  small  scale  of  iodine,  and  cork 
the  mouth  of  the  tube.  Set  aside  for  a  day 
in  a  warm  place.  The  iodine  volatilizes  and 
combines  with  the  mercury,  forming  a  red  com- 
pound, mercuric  iodide. 

D.  Amalgamate  zinc  by  dipping  it  into  mer- 
cury. Heat  a  piece  of  the  amalgamated  zinc  in 
a  tube  and  collect  the  mercury  given  off.  Drop 
another  piece  of  the  amalgamated  zinc  into  di- 


440  DENTAL    CHEMISTRY. 

lute  sulphuric  acid,  and  notice  that  little  or  no 
hydrogen  is  given  off. 

E.  Heat  mercuric  nitrate  in  a  porcelain  dish 
placed  in  a  current  of  air  until  red  fumes  no 
longer  pass  off.  A  red  powder  remains  which 
is  mercuric  oxide: — 

Hg(N03)a+  heat  =HgO+2NO,+0 
Continue  the  heating  and  the  mercuric  oxide  is 
decomposed,  thus: — 

HgO=Hg+0 

F.  To  illustrate  the  formation  of  mercurous  ni- 
trate proceed  as  follows:— heat  about  one 
gramme  of  mercury  with  2  c.c.  of  nitric  acid 
until  no  further  reddish  fumes  are  seen.  Mer- 
cur^//5  nitrate  is  formed  as  follows:— 

6Hg+8HN03=3[(Hg,(N03)3]+4H,0+2NO 
If  some  of   the    mercury    remains  undissolved, 
the  solution  deposits  crystals  of  the  mercurous 
nitrate  on  cooling. 

G.  To  prepare  mercuw  nitrate  take  some 
of  the  solution  obtained  in  F,  or  some  of  the 
crystals,  and  heat  with  an  equal  weight  of  ni- 
tric acid  till  reddish  fumes  are  no  longer 
given  off.  The  solution  should  give  no  pre- 
cipitate with  hydrochloric  acid;  if  it  does,  heat 
with  more  nitric  acid  until  hydrochloric  acid 
ceases  to  give  precipitate.  Then  evaporate  sol- 
ution and  set  aside  for  crystallization.  Mercuw 
nitrate  is  formed  according  to  the  equation:— 


EXPERIMENTAL    CHEMISTRY.  441 

3[Hg.(N03)J+8HN03=6[Hg(N03(J 
+4H,0+2NO 

Exercise  60.  Arsenic:— 

A.  Mix  any  compound  of  arsenic  with  char- 
coal and  dry  potassium  carbonate  in  a  long 
narrow  tube,  and  notice  the  deposit  of  metal- 
lic arsenic  as  a  ring  in  the  upper  part  of  the 
tube. 

B.  Heat  a  little  arsenous  oxide  in  an  ignition 
tube,  and  examine  the  sublimate  formed  with 
the  microscope.  Octahedral  crystals  will  be  ob- 
served. 

C.  Note  the  repellent  action  of  arsenic  on 
water,  by  causing  arsenic  in  fine  powder  to  float 
on  the  surface  of  water. 

D.  Heat  arsenous  oxide  on  a  piece  of  charcoal 
with  the  blow  pipe,  and  note  the  odor  of  gar- 
lic. 

Exercise  61.  Antimony:— 

A.  Boil  a  little  black  antimony  sulphide  in 
about  1 0  c.c.  of  hydrochloric  acid  until  most  of 
it  is  dissolved. 

Antimony  chloride  is  formed  and  remains  in 
solution,  according  to  the  equation 

Sb,S3+6HCl=3H,S+2SbCl3. 
Let  settle,  pour  off  the  clear  solution,  evaporate 
to  about    half  its  volume  and  add  to  100  c.c. 
water.    A  white  precipitate    of  oxychloride  of 


442  DENTAL    CHEMISTRY, 

antimony  (powder  of  Algaroth)  takes  place,  ac- 
cording to  the  equation 

1 2SbCl3+ 1 5  H,0=2SbCl3.5Sb  A+30HCI 
Let  settle,  decant,  add  water  again,  let  settle  again 
and  decant.    Now  add  to  the  washed  oxychloride 
an  aqueous  solution  of  a  little  sodium  carbonate, 
about  1  gramme.    The  oxychloride  is  converted 
into  the  oxide  according  to  the  equation 
2SbCl3.5Sb303+3Na.C03= 
6SbA+6NaCl+3CO,. 
Collect  on  a  filter  after  effervescence  is  over,  wash, 
and  treat  while  still  moist  with  solution  of  pot- 
assium acid  tartrate.     Tartar  emetic  is  formed 
according  to  the  equation 

2KHC,H,06+Sb,03=2KSbO.QH,06+H,0 

Tartar  emetic  is  an  organic  compound.  See  page  300. 

Exercise  62.  Gold:— 

A.  Test  the  insolubility  of  gold  in  hydrochloric, 
nitric,  and  sulphuric  acids. 

B.  Go  back  to  Exercise  16  (Nascent  State)  and 
make  solution  of  auric  chloride.  (Use  this 
time  2  to  4  drops  nitric  acid,  5  or  10  drops  hy- 
drochloric, and  a  small  piece  of  gold  leaf). 

C.  Make  a  solution  of  ferrous  chloride,  as  in 
Exercise  51,  and  add  about  one  c.c.  of  it  to  the 
solution  made  in  B.  Note  the  precipitate  of 
metallic  gold. 


CHEMICAL  ANALYSIS  443 


CHAPTER  VIII. 

CHEMICAL    analysis:    THE    BLOW-PIPE. 

2.    Next  study  the  blow-pipe  and  its  use. 

536.  The  blow-pipe,  as  commonly  used,  is  a  small, 
hollow,  cylindrical,  brass  instrument,  curved  at  the 
narrower  end;  it  serves  to  conduct  a  continuous,  fine 
current  of  air  into  a  gas  flame,  or  into  the  flame  of  a  candle 
or  lamp.  [Various  improvements  on  the  ordinary  instru- 
ment have  been  devised;  for  example,  the  trumpet  mouth 
piece,  so  called,  is  used  so  that  the  muscles  of  the  lip  may 
not  be  fatigued.  Fletcher's  blow-pipe  is  highly  recom- 
mended by  Essig  for  work  in  the  dental  laboratory;  in 
this  instrument  the  air-tube  is  coiled  into  a  light  spiral, 
over  the  point  of  the  jet]. 

537.  If  the  ordinary  blow-pipe  is  used,  the  beginner 
must  practice  blowing  a  steady  current  through  the  blow- 
pipe zi'it/i  tJic  checks  and  not  with  the  lungs.  Distend  cheeks, 
take  the  blow-pipe  between  the  lips,  and  practice  quiet 
breathing  for  some  little  time.  When  sufficient  readiness 
in  producing  the  current  is  thus  acquired,  bring  the  blow- 
pipe to  a  flame  and  practice  on  what  are  called  the  re- 
ducing ilanie  and  the  oxidizing  flame.  Note:  a  flame  of 
gas,  candle,  or  lamp,  consists  of  three  parts,  (a)  a  dark 
nucleus    in  the  centre,  (b)  a  luminous    cone    surrounding 


444 


DENTAL    CHEMISTRY. 


nucleus,  and  (c)  a  feebly  luminous  mantle  encircling  the 
whole  flame.     Fig.  4. 

538.  The  reducing  flame  is  produced  by  keeping  the 
jet  of  the  blow-pipe  just  on  the  border  of  a  tolerably  strong 
gas  flame,  and  driving  a  moderate  blast  across  it:  the 
resulting  mixture  of  the  air  with  the  gas  is  only  imperfect 
and  there  remains,  between  the  inner  bluish  part  of  the 
flame,  and  the  outer  barely  visible  part,  a  luminous  and 
reducing  zone,  of  which  the  hottest  point  lies  somewhat 
beyond  the  apex  of  the  inner  cone.  This  flame 
serves,  under  certain  circumstances  hereafter  to 
be  explained,  to  take  away  oxygen  from  a  metallic 
compound,  i.e.  to  reduce  it. 

539.  The  oxidizing  flame  is  produced  by  low- 
ering the  gas,  pushing  the  jet  of  blowpipe  a  little 
farther  into  the  flame,  and  increasing  the  strength 
of  the  current.     This  serves  to  effect  an  intimate 


Fig.  5.  Fig.  4. 

mixture  of  the  air  and  gas,  and  an  inner,  pointed,  bluish 
cone,  slightly  luminous  towards  the  apex,  is  formed,  and 
surrounded  by  a  thin,  pointed,  light-bluish,  barely  visible 
mantle.  The  hottest  part  of  the  flame  is  at  the  apex  of 
the  inner  cone.  Difficultly  fusible  bodies  are  exposed  to 
this  part  to  effect  their  fusion;  but  bodies  to  be  oxidized 
are  held  a  little  beyond  the  apex,  that  there  may  be  no 
want  of  air  for  their  combustion.  For  an  oxidizing  flame, 
a  small  spirit  lamp  will  in  most  cases  be  sufficient.    Fig.  5. 


CHEMICAL    ANALYSIS.  445 

540.  Charcoal  is  used  for  reducing  processes:  the  sub- 
stances to  be  operated  on  are  put  into  small  cavities  in  it, 
scooped  out  with  a  penknife,  and  the  reducing  flame  of 
the  blowpipe  is  directed  upon  them.  The  fusibility  of 
bodies  is  also  ascertained  by  use  of  charcoal  as  a  support. 
Incrustations  are  often  formed  on  the  charcoal,  composed 
of  an  oxide  formed  after  reduction,  when  the  metallic 
fumes  pass  through  the  outer  flame,  and  become  re-oxidizcd. 
Many  incrustations  have  characteristic  colors,  leading  to 
the  detection  of  metals. 

541.  Pliitiniim  wire  and  sometimes  platinum  foil  are 
used  for  oxidizi^ig  processes,  and  also  when  fusing  sub- 
stances with  fluxes,  in  order  to  obtain  what  is  called  a 
head,  etc.,  etc.  The  wire  is  cut  into  convenient  lengths, 
say  8  centimetres  (a  little  over  3  inches)  and  twisted  at 
both  ends  into  a  small  loop.  When  required  for  use,  the 
loop  is  moistened  with  a  drop  of  water,  then  dipped  into 
the  powdered  flux — if  any  is  to  be  used,  and  the  portion 
adhering  fused  in  the  flame  of  a  gas  or  spirit  lamp. 
When  the  bead  produced,  which  sticks  to  the  loop,  is  cold 
it  is  moistened  again,  and  a  small  portion  of  the  substance 
to  be  examined  is  put  on,  and  made  to  adhere  to  it,  by 
the  action  of  gentle  heat.  The  loop  is  then  exposed  to 
whatever  flame  is  desired. 

[Many  kinds  of  supports  have  been  devised,  but  when 
a  small  quantity  of  gold  or  silver  is  to  be  melted  in  the 
dental  laboratory,  the  operation  is  usually  performed  on 
a  support  made  of  charcoal.  Essig  recommends  that  a 
good,  solid,  cylindrical  piece  of  thoroughly  charred  pine 
coal  be  cut  in  halves  vertically,  by  means  of  a  saw.  On 
the  end  of  one  half,  a  depression  is  cut  for  the  recep- 
tion of  the  metal  to  be  melted,  and  on  the  flat  side 
of  the  other  half,  extending  to  the  end,  the  ingot 
mould  is  carved.  The  two  halves  are  tied  together  with 
wire  J. 


446 


DENTAL    CHEMISTRY. 


542.  The  simplest  self-acting  blowpipe  is  really  the 
Bunsen  gas-lamp,  provided  with  a  chimney.  The  flame 
is  non-luminous,  and  burns  without  soot;  Bunsen  distin- 
guishes six  parts  to  the  flame:  the  dase  near  where  the  gas 
escapes  from  the  hnrner,  the  fusing  zone  about  one-third 
of  the  height  of  the  flame  from  the  bottom,  and  equi- 
distant from  the  outside  and  inside,  the  lower  oxidizing 
flame  on  the  outer  border  of  the  fusing  zone,  the  upper 
oxidiziyig flame ,  which  is  the  non-luminous  tip  of  the  flame, 
the  lower  reducing  zone  in  the  inner  border  of  the  fusing 
zone,  the  upper  reducing  flame  in  the  luminous  tip  of  the 
dark  inner  cone.  Many  substances  give  characteristic 
tints  to  a  colorless  flame  like  the  Bunsen.  For  instance, 
salts  of  sodium  impart  to  flame  a  yellow  tint,  potassium 
a  violet,  lithium  a  carmine,  etc.,  etc. 

3.  Having  become  familiar  with  the  use  of  the  blow- 
pipe, the  structure  of  flame,  etc.,  etc.,  take  a  port-on  of 
the  substance  to  be  examined,  place  it  with  an  equal 
weight  of  sodium  carbonate  in  a  little  cavity  in  the  char- 
coal, and  expose  for  some  minutes  to  the  inner  or  reducing 
flame  of  the  blow-pipe. 

543.  The  following  table*  will  serve  to  aid  in  the 
interpretation  of  results: 

Cu.  Au.  Ag. 

A      red     bead,        A  yellow  bead,         A   white,    maf- 
somewhat      diffi-    easily    malleable,     leable  bead.      No 
cult  to  fuse.     No     No  incrustation.       incrustation, 
incrustation. 

Pb.  Sn. 

Grayish-white  White  globules, 
globule,  with  yel-  not  so  readily  re- 
low  incrustation,  duced  as  Pb;  mal- 
Very  soft.  leable.     Incrusta- 

tion yellowish 
when  hot,  white 
when  cold. 


Sb. 
Gray,  brittle  glob- 
ules   which    readily 
oxidize    when    hot. 
White   incrustation. 


*01dberg  and  Long. 


CHEMICAL    ANALYSIS. 


447 


544.    Short  method  for  blow-pipe  analysis. 

I.  Heat  on  charcoal  equal  weights  of  the 
substance  to  be  examined  and  sodium  car- 
bonate. Use  inner  or  reducing  blow-pipe 
flame.  Notice  odor,  metallic  globule,  incrusta- 
tion. [If  none,  go  on  with  II],  If  a  result  is 
apparent,  consult  the  following  table: 


Metallic  globules.     Incrustation.        Probable  metal. 
Very  brittle.        White.  Antimony. 


None, 
Brittle, 


White, 
Yellow. 


Arsenic, 
Bismuth, 


Red,  malleable.  Little  or  none.  Copper. 

Soft,  malleable.  Yellow.  Lead. 

Malleable.  Little  ornone.  Silver, 


Malleable, 


None, 


Little  ornone.  Tin. 


Yellow  when    Zinc, 
hot,  white 
when  cold. 


Remarks, 

Metal  volatil- 
izes. 

Garlic  fumes. 

Metal  easily 
fused. 

Difficult  to 
fuse. 

Marks  paper. 

Not  oxidiza- 
ble. 

Easily  oxidiz- 
ed and  easily 
fused, 

Infusible,mass 
greenish- 
white. 


Antimony  gives  off  white  fumes,  and  covers  charcoal 
with  incrustation.  If  arsenic  is  suspected,  proceed  as  in 
V,  If  bismutli  is  apparently  the  metal,  confirm  as  fol- 
lows: heat  a  portion  of  the  original  substance  on  charcoal 
with  a  mixture  of  equal  parts  sulphur  and  potassium 
iodide:  bright  red  incrustation  on  the  cooler  part  indicates 
bismuth. 

Copper  may  first  be  seen  in  the  form  of  a  reddish-brown 
substance,  after  heating  in  the  inner  flame.  Now  heat»in 
the  point  of  the  blue  inner  flame,  and  a  metallic  globule 
of  tough    copper  is  obtained.     If  the  substance  is  brass^ 


448  DENTAL   CHEMISTRY. 

a  yellow  incrustation  of  oxide  of  zinc  will  be  seen  when 
the  substance  is  hot,  becoming  white  on  cooling. 

Lead  may  readily  be  recognized  by  its  metallic  globule 
of  considerable  size;  the  globule  is  soft,  and  may  readily 
be  flattened  with  a  knife  or  cut.  If  the  lead  contain  silver, 
the  latter  is  detected  by  the  use  of  bone-ash.  Fill  a 
bowl-shaped  cavity  in  the  charcoal  with  finely  powdered 
bone-ash,  pressed  down  well  so  as  to  fill  the  cavity  with 
a  compact  mass,  smooth,  and  slightly  hollowed  on  the 
surface.  In  this  bone-ash  place  a  small  piece  of  the  lead, 
hold  the  charcoal  horizontally,  and  direct  the  extreme 
point  of  the  outer  (oxidizing)  flame  upon  the  metal. 
The  bone-ash  absorbs  the  lead  oxide  formed,  leaving  a 
metallic  globule  of  silver;  the  latter  may  be  covered  with 
a  thin  film  of  oxide,  showing  rainbow  tints.  When  the 
colors  cease,  and  the  globule  no  longer  diminishes  in  size, 
it  is  pure  silver.  The  process  is  hindered  by  presence  of 
tin. 

Silver  is  easily  reduced,  but  not  readily  fused  to  a  glo- 
bule. Sharp  heat  is  required  to  accomplish  the  latter. 
When  the  globule  is  once  formed,  it  is  easily  distinguished 
from  all  other  metals  by  the  fact  that  it  retains  a  bright 
metallic  surface,  when  fused  at  the  point  of  the  outer  (oxi- 
dizing) flame,  and  shows  a  characteristic  white  color. 

If  tin  be  suspected,  take  a  fresh  quantity  of  the  origi- 
nal substance  and  heat  with  potassium  cyanide  instead  of 
sodium  carbonate.  A  very  liquid  slag  is  obtained,  in 
which  a  large  globule  of  tin  may  be  formed  without 
difficulty. 

Zinc  is  so  readily  volatilized,  i.  e.,  converted  into  vapor, 
by  heat  that  no  metallic  globule  is  formed,  but  merely  a 
yellow  incrustation.  Moisten  the  latter  w4th  a  dilute 
soiution  of  cobalt  nitrate,  heat  strongly,  and  ^  green  com- 
pound (of  zinc  and  cobalt)  is  formed. 

II.     If  nothing  be  found  by  proceeding  as 


CHEMICAL    ANALYSIS.  ,  449 

in  I,  take  a  very  little  of  the  substance,  reduce 
to  powder,  heat  on  borax  bead,  in  a  loop  of 
platinum  wire,  in  the  outer  (oxidizing-)  flame. 
Note  the  color  when  hot,  let  cool,  and  observe 
the  color.  Now  expose  to  inner  flame,  noting: 
color  when  hot  and  when  cold,  as  before. 
Then  consult  the  following;  table: 

Metals.  Outer   Flame.  Inner  Flams. 

Chromium.  Yellowish  green.  P.merald  green. 

Cobalt.  Blue.  Blue. 

Copper.  Blue.  Brown  or  colorless. 

Iron.  Brownisn  yellow.  Bottle  green. 

Manganese.  Purple  or  pink.  Colorless. 

Nickel.  Brownish  yellow.  Muddy  gray. 

III.  If  nothing  distinct  has  been  noted  in 
procedure  as  by  ii,  moisten  a  clean  platinum 
wire  with  HCl,  take  a  very  little  of  the 
powdered  substance  on  it,  expose  to  inner 
blow-pipe  flame.  Observe  any  distinct  color 
which  may  be  imparted  to  outer  flame.  Con- 
sult the  following-  table: 


Metal. 

Color  imparted  to  outer  flame. 

Barium. 
Calcium, 

Green. 
Red. 

Copper. 
Potassium. 
Sodium. 
Strontium. 

Bluish-green. 
Violet-blue. 
Yellow. 
Carmine. 

IV.  If  no  distinct  color,  other  than  yellow, 
be  observed  in  in,  proceed  now  as  follows: 
heat  a  little  of  the  powdered  substance  on 
charcoal   at  the   point  of  the  inner  blow-pipe 


450  DENTAL     CHEMISTRY. 

flame,  until  it  leaves  an  infusible  residue. 
Moisten  this  residue  with  a  drop  or  two  of 
cobalt  nitrate.  Heat  strongfly  in  point  of 
inner  flame.     Consult  the  following  table: 


Metal. 

Appearance. 

Aluminium. 

Blue  mass. 

Zinc. 

Green  mass. 

Magnesium. 

Pink  mass. 

V.  Finally,  if  no  color  has  been  obtained 
by  proceeding"  as  in  iv,  mix  a  little  of  the 
powdered  substance  with  dried  sodium  car- 
bonate and  a  little  charcoal,  pour  into  a  small 
tube  closed  at  one  end  and  heat.  Consult  the 
following  table: 

Metal.  Result. 

Mercury.  Minute,    gray     globules,     con- 

densed on  cooler  part  of  the 
tube. 

Arsenic.  Shiny,  black  sublimate. 

Ammonium  compounds.    Odor   of   ammonia    given    off. 

(Bloxam). 


CHEMICAL   ANALYSIS.  451 


CHAPTER  IX. 

CHEMICAL    analysis:    REACTIONS    OF   THE    METALS. 

A.  Compounds  of  Silver. 

545.  Dissolve  5  grammes  of  silver  nitrate  in 
100  c.c.  of  distilled  water  in  a  beaker.  When  all 
is  dissolved,  pour  the  clear  solution  into  an 
amber-colored  bottle,  cork,  and  label. 

Of  the  solution  thus  made  pour  5  c.c.  into  two  differ- 
ent, clean,  dry  test-tubes,  and  add  to  each  tube  solutions 
of  the  following  reagents  in  order:— 

I.     To  the  first  add  pure  hydrochloric  acid,  plentifully, 
say  5  c.c,  or  solution  of  any  soluble  chloride,  as  common 
salt.    Shake  well,  and  set  aside.     A   heavy,    curdy,  white 
precipitate  is  formed,  silver  (argentic)  chloride*. 
AgN03+HCl=AgCl+HN03. 

Let  settle,  decant,  pour  precipitate  in  equal  parts  into 
four  clean  test-tubes,  add  (plentifully)  nitric  acid  to  one, 
ammonia-water  to  another,  solution  of  potassium  cyan- 
ide to  the  third,  and  expose  the  fourth  to  the  sunlight. 
Shake  the  first  three  tubes  well,  and  observe  what  happens 

*The  instructor  should  propound  problems  in  chemical  arithmetic  based    on  the 
equations  given.    The  student  should  be  required  to  explain  the  equations. 


452  DENTAL    CHEMISTRY. 

as  follows:  the  first  precipitate  is  undissolved,  the  second 
and  third  are  dissolved;  the  fourth  turns  violet  after  a 
time. 

These  experiments  show  that  a  soluble  salt  of 
silver,  as  the  nitrate,  when  dissolved  in  water 
gives  a  white  curdy  precipitate  with  hydrochloric 
acid,  insoluble  in  nitric  acid,  soluble  in  ammon- 
ium hydroxide,  and  solution  of  potassium  cyan- 
ide, and  turned  violet  by  the  sunlight. 

2.  To  the  second  tube  containing  solution  of  silver 
nitrate  add  either  solution  of  hydrogen  (hydric)  sulphide, 
HgS,  (sulphuretted  hydrogen, sulphydric  acid)  or  ammon- 
ium sulphide  (sulphydrate):  a  black  precipitate,  silver 
(argentic)  sulphide  is  formed: — 

2AgN03+H2S=:2HN03+Ag,S. 

B.  Compounds  of  Lead:— 

Dissolve  5  grammes  of  lead  nitrate  in  100  c.c. 
of  water,*  pour  the  solution  in  equal  parts  into 
two  test-tubes,  5  c.c.  in  each,  and  test  as  follows: 

1.  To  the  first  test-tube  add  plenty  of  pure  hydro- 
chloric acid,  or  solution  of  soluble  chloride:  a  white  pre- 
cipitate is  formed,  lead  chloride,  PbClj  as  follows: — 

Pb(N03)2+2HCl=2HN03-j-PbCl2. 
The  precipitate  is  not  affected  by  light.  Pour  the  pre- 
cipitate in  equal  parts  into  three  clean  test-tubes:  boil  one 
and  it  dissolves.  Pour  a  little  of  the  contents  of  the  sec- 
ond into  a  large  beaker  full  of  water,  and  it  is  dissolved.  To 
the  third  add  ammonia- water:  it  is  not  dissolved.  In  other 
words  the  precipitate  is  not  entirely  insoluble,  hence  is 
not  formed  in  dilute  solutions. 

2.  To  the  second  test-tube,  with  or  without  hydro- 
chloric acid,  add  solution  of  hydric  sulphide  or  (without 

♦Save  any  not  used,  for  future  work. 


CHEMICAL    ANALYSIS.  453 

HCl)  ammonium  sulphide;  if  strong  solution  of  the  above 
is  added  plentifully,  a  black  precipitate  of  lead  sulphide, 
PbS  is  formed; — 

Pb(N03)2+H,S=2HN03+PbS) 
(If  the  lead  solution  contains  much  hydrochloric  acid,  a 
red  precipitate  is   formed,    PbClj+SPbS,    converted    into 
PbS  on  further  addition  of  H2S) 

Warm  the  tube  containing  the  black  precipitate,  let 
settle,  decant,  and  treat  the  precipitate,  divided  into  two 
equal  parts,  with  hot,  strong  nitric  acid,  and  hot  hydro- 
chlojic  acid.  The  nitric  acid  decomposes  the  precipitate 
forming  nitrate  or  sulphate  of  lead,  or  both,  according  to 
strength  of  acid  used.     Thus 

3PbS+8HNO,=3Pb(N03)2+4H20+2NO+3S 
if  the  acid  is  dilute;  or 

3PbS+8HN03=3PbSO,+8NO 
if  the  acid  is   fully   concentrated.  The  precipitate  is    not 
affected  by  hydrochloric  acid. 

The  above  tests  are  sufificient  to  recognize  even  small 
quantities  of  lead;  in  the  case  of  very  dilute  solutions  a 
current  of  washed  sulphuretted  hydrogen  gas  is  passed 
into  the  acidulated  solution  to  be  tested.  Lead  in  min- 
ute quantities  in  drinking  water  is  thus  detected  by  a 
brownish  precipitate,  which  settles  in  the  course  of  a  day 
or  so. 

C.  Mercuroiis  Compounds. 

Dissolve  5  grammes  of  mercurous  nitrate 
crystals  in  45  c.c.  of  water,  to  which  5  c.c.  of 
nitric  acid  have  been  added.  Pour  the  solution 
thus  made  in  equal  parts  into  two  test-tubes, 
5  c.c.  in  each,  and  test  as  follows: — 

I.     To  the  first  test-tube   add  a   drop   or    two  of   pure 


454  DENTAL    CHEMISTRY. 

hydrochloric  acid  or  solution  of  soluble  chloride;  shake 
the  tube,  and  a  white  precipitate  mercurous  chloride,  is 
formed: 

Hg,(N03)2+2HCl=2HN03+Hg,Cl,. 
Add  water  till  the  tube  is  half  full,  and  then    further  add 
ammonia  water  and  mix  well:  the  precipitate  blackens. 

The  white  precipitate  formed  with  hydrochlo- 
ric acid  is  calomel.  Addition  of  ammonia  water 
converts  it  into  mercurous-ammonium  chloride, 
NH,Hg,Cl. 

2.  To  the  second  test-tube  add  solution  of  hydric  sul- 
phide or  ammonium  sulphide:  a  black  precipitate  is  formed 
which  is  mercuric  sulphide  and  mercury,  HgS.Hg,  thus: — 
Hg2(N03)2+H,S=2HN03+HgS+Hg 

Let  the  precipitate  settle,  decant,  treat  precipitate  with 
warm,  dilute  nitric  acid,  and  it  is  not  dissolved.  Treat  an- 
other portion  of  the  precipitate  with  ammonia  water  and 
ammonium  sulphide,  and  it  is  not  dissolved. 

D.  Mercuric  Compounds:— 

546.  Dissolve  2  grammes  of  mercuric  chloride, 
(corrosive  sublimate)  in  100  c.c.  of  water.  Pour 
the  solution  in  equal  parts  into  eight  test-tubes, 
5  c.c.  in  each,  and  test  as  follows: 

1.  To  the  first  tube  add  plenty  of  pure  hydrochloric 
acid:  no  precipitate  is  formed. 

2.  To  the  second  tube  add  hydrochloric  acid  as  above, 
and  also  solution  of  sulphuretted  hydrogen  (or  ammon- 
ium sulphide  without  hydrochloric  acid).  A  mottled 
precipitate  is  formed  which  may  be  white  or  gray  at 
first,  then  yellow  or  orange,  and  finally  black,  when 
sufficient  strong  solution  of  sulphuretted  hydrogen  is 
added.     The    change    in    colors  is    best  seen  by  adding 


CHEMICAL   ANALYSIS.  455 

iittle  of  the  reagent  at  a  time,  and  shaking.  The  whitish 
precipitate  is  a  combination  of  the  sulphide  and  the 
undecomposed  chloride,  PigCl2+2HgS;  the  final  black 
precipitate  is   mercuric   sulphide,    HgS,  thus: — 

HgCI,+H,S^HgS+2HCl 
Let  the  precipitate  settle,  decant,  and  treat  residue  with 
warm,  dilute  HNO3,  and  it  is  not  dissolved. 

3.  To  the  third  test-tube  add  cautiously  a  drop  or 
two  of  solution  of  potassium  iodide: — a  yellow  precipitate, 
mercuric  iodide,  Hgia,  quickly  turning  scarlet-red,  is 
formed.     Shake  the  tube:  the  precipitate  disappears, 

HgCl2+2KI=Hgl2+2KCl. 

4.  To  the  fourth  tube  add  plenty  of  solution  of  sodium 
or  potassium  hydroxide: — a  yellow  precipitate  of  mer- 
curic oxide  is  formed: — 

HgCl2+2KHO=HgO+2KCl-fH20. 

5.  Add  the  contents  of  the  fifth  tube  to  ammonia-water, 
taking  care  that  the  mixture,  after  stirring  well,  still 
smells  of  ammonia;  a  white  precipitate  is  formed,  mer- 
curic-ammonium chloride,  NHoHgCl,  that  is,  ammonium 
chloride,  NH^Cl,  in  one  molecule  of  which  two  univa- 
lent atoms  of  hydrogen  are  substituted  by  one  bivalent 
atom  of  mercury: — 

HgCl2+2NH,HO=NH2HgCl+NH,Cl-f:^H,0 

6.  To  the  sixth  test-tube  add  solution  of  potassium 
chromate: — a  yellowish-red  precipitate,  mercuric  chromate 
is  formed. 

7.  To  the  seventh  tube  add  solution  of  sodium  or 
potassium  carbonate: — a  brownish-red  precipitate  of  basic 
mercuric  carbonate,  HgCOs.SHgO,  is  formed. 

8.  Into  the  eighth  tube  dip  a  piece  of  copper  wire,  and 
it  becomes  white  from  deposition  of  mercury.  This  react- 
ion is  the  same  for  mercurcw^   compounds  also. 

Furthermore,  heat  dry  mercuric    chloride  on  platinum 


456  DENTAL    CHEMISTRY. 

foil  and  notice  that  it  is  volatilized.  If  the  experiment 
be  performed  in  a  test-tube  with  charcoal  and  sodium 
carbonate,  a  mirror  of  sublimed  mercury  will  be  formed 
on  the  sides  of  the  tube. 

E.  Compounds  of  Copper:— 

Make  a  solution  of  5  grammes  of  cupric  sul- 
phate in  100  c.c.  of  water,  rubbing  up  in  the 
mortar  to  hasten  solution.  The  solution  is  blue, 
and  turns  blue  litmus  red.  Pour  5  c.c.  of  this 
solution  into  each  of  seven  test-tubes,  and  test 
as  follows : — 

1.  To  the  first  tube  add /«r^  hydrochloric  acid  plenti- 
fully.    No  precipitate  is  formed. 

2.  To  the  second  tube  add  hydrochloric  acid  as  above 
and  strong  solution  of  sulphuretted  hydrogen  plentifully 
(or  a  few  drops  of  ammonium  sulphide  to  the  solution 
without  hydrochloric  acid):  a  brownish-black  precipitate, 
cupric  sulphide,  CuS,*is  formed: 

CuSO,+H2S=H2SO,-fCuS. 
Warm  the  tube,  let  settle,  decant,  pour  the  precipitate  in 
equal  parts  into  two  test-tubes,  add  a  little  nitric  acid  to 
one,  hydrochloric  to  the  other,  and  boil  both.  The  cup- 
ric sulphide  dissolves  in  nitric  but  not  in  hydrochloric 
acid.  In  the  nitric  acid  solution  may  be  seen  a  scum  of 
grayish  sulplmr. 

3.  To  the  third  test-tube  add  sodium  or  potassium  hy- 
droxide: a  blue  precipitate  is  formed,  cupric  hydroxide, 
Cu(HO)2;  boil,  and  the  hydrate  is  decomposed, becoming 
black  anhydrous  oxide,  CuO. 

4.  To  the  fourth  test-tube  add  a  few  drops  of  ammonia- 
water  without   shaking: — a  blue    precipitate  is  formed. 


'Insoluble  in  ammonium  sulphide. 


CHEMICAL   ANALYSIS.  457 

cupric  hydroxide,  Cu(HO)2;  add  ammonia- water  plenti- 
fully, and  the  precipitate  is  dissolved,  forming  an  azure- 
blue  solution,  containing  an  ammonio-copper  compound. 

5.  Pour  out  the  solution  in  the  fifth  tube,  and  without 
cleaning,  draining,  or  letting  dry,  fill  with  water,  and  add 
a  drop  of  ammonia-water.  Shake  well,  and  a  faint  blue 
color  is  seen,  showing  the  delicacy  of  the  test.  The  few 
drops  of  copper  solution,  adhering  to  the  inside  of  the 
tube,  are  suf^cient,  even  when  largely  diluted,  to  react 
with  a  single  drop  of  ammonia-water. 

6.  Perform  the  same  test  as  in  5  and  in  the  same  way 
using,  however,  solution  of  potassium  ferrocyanide,  instead 
of  ammonia;  a  reddish-brown  precipitate,  cupric  ferrocy- 
anide, Cu2Fe(CN)6  is  formed. 

7.  Into  the  seventh  tube  dip  the  point  of  a  pen-knife, 
after  adding  a  drop  of  hydrochloric  acid.  The  knife  be- 
comes coated  with  copper: — 

CuSO,+Fe     FeSO^+Cu 

F.  Compounds  of  Bismuth:— 

Dissolve  about  7  grammes  of  crystallized  ni- 
trate of  bismuth,  Bi(N03)3  in  15  c.c.  of  strong 
nitric  acid,  and  dilute  with  water  to  make  100  c.c. 
Pour  5  c.c.  into  each  of  three  c/ry  test-tubes, 
and  test  as  follows: — 

1.  To  the  first  tube  add  lo  drops  of  hydrochloric  acid, 
or  10  drops  of  strong  solution  of  sodium  chloride,  and  no 
precipitate  appears.  The  solution  should  be  clear  before 
the  acid  is  added. 

2.  To  the  second  tube  add  directly  strong  solution  of 
sulphuretted  hydrogen  or  ammonium  sulphide: — a  dark- 
brown  precipitate,  bismuth  sulphide,  BiaSg,  is  formed: — 

2Bi(N03)3-t-3H2S=Bi2S3+6HN03 
Let  precipitate  settle,    decant,  add  ammonia- water  and 


458  DENTAL    CHEMISTRY. 

ammonium  sulphide,    and  precipitate    is  not  dissolved. 
(Differentiation  from  arsenic  and  antimony). 

3.     Take  up  water  in  a  nipple  pipette  and  let  it   trickle 

down  the  side  into  the  contents  of  the  third  tube:  a  white 

precipitate,  bismuthyl  oxynitrate,  BiONOs.HjO,  is  formed: 

5(Bi3N03)+8H20= 

4(BiON03.H20)+Bi3N03;8HN03. 

The  liquid  contains  bismuth  nitrate  in  acid. 

547.  G.  Arsenous  Compounds:— 

I.  Boil  1  gramme  of  white  arsenic,  AS2O3,  in  a 
solution  of  2  grammes  of  pure  hydrochloric  acid 
in  25  c.c.  of  distilled  water,  until  the  arsenic  is 
dissolved.  Filter,  and  pass  enough  distilled 
water  through  the  filter  to  make  1 00  grammes 
by  weight.  N.  B.  For  analytical  purposes  100 
c.c.  will  suifice.  The  solution  made  by  weight 
as  above  is  the  Liquor  Acidi  Arsenosi  of  the 
U.  S.  P. 

Pour  5  c.c.  of  the  solution  into  each  of  three 
test-tubes  and  test  as  follows: — 

1.  To  the  first  test-tube  add  pure  hydrochloric  acid 
plentifully.     No  precipitate  is  formed. 

2.  To  the  second  add  hydrochloric  acid,  as  above, 
and  strong  solution  of  sulphuretted  hydrogen  plentifully. 
A  bright,  lemon-yellow  precipitate  is  formed,  arsenous 
sulphide,  or  trisulphide.  As  2S3: — 

As203+3H2S=:3H20+As2S3 
If  it  is  true  that,  when  white  arsenic  is  dissolved  in  water» 
arsenous  acid  is  formed,  we  have 

As203+3H20=2H3As03 
in  which  case,  when  sulphuretted  hydrogen  is  added,  we 
have 


CHEMICAL   ANALYSIS  459 

2H3As03+3H2S=6H20+As2S3 
Let  the  precipitate  settle,  decant,  divide  into   two   parts, 
and  treat  with  ammonium  sulphide,    and  strong    hydro- 
chloric acid  respectively.     It  dissolves  in  the  first  but  not 
in  the  second. 

3.  To  the  third  test-tube  add  ammonium  sulphide: 
result  same  as  in  2. 

Note:  it  is  absolutely  necessary,  in  order  that  tests  2 
and  3  may  succeed,  that  the  solution  of  arsenic  to  be  tested 
contain  free  acid,  as  hydrochloric. 

II.  Next  warma  little  white  arsenic  in  a  test- 
tube  full  of  water  for  about  1 5  minutes.  Pour 
half  the  solution  obtained  into  another  test-tube 
and  proceed  as  follows: 

To  one  of  these  last  two  tubes  add  a  few  drops  of  a 
solution  of  argentic  nitrate:  further  add  a  few  drops  of 
diluted  ammonia  water,  one  drop  at  a  time  until  the  solu- 
tion is  neutral;  a  yellow  precipitate  is  formed,  silver 
arsenite,  Agg  As  O3;  add  more  ammonia-water,  and  the  pre- 
cipitate is  dissolved. 

To  the  other  tube  containing  the  solution  of  arsenic  in 
water,  add  a  few  drops  of  a  solution  of  cupric  sulphate, 
and  then  dilute  ammonia-water  as  before:  a  green  precip- 
itate, cupric  arsenite,*  CuHAsOg,  is  formed.  Add  more 
ammonia  water,  and  the  precipitate  is  dissolved  with  for- 
mation of  a  blue  color. 

N.  B.  It  is  absolutely  necessary  for  the  success  of  these 
last  two  tests,  that  the  solution  containing  arsenic  be  of 
neutral  reaction,  as  the  precipitates  are  soluble  in  both 
acids  and  alkalies. 

II.  Arsenic  Compounds.  (Arsenates). 

Dissolve    5    grammes    of    sodium     arsenate. 


*Known  as  Scheele's  green. 


460  DENTAL   CHEMISTRY. 

Na^H  As  O4,  in  100  c.c.  of  water.  Pour  5  c.c.  of 
the  solution  into  each  one  of  six  test-tubes  and 
test  as  follows: — 

1.  To  the  first  tube  add  hydrochloric  acid  plentifully. 
No  precipitate  is  formed. 

2.  To  the  second  tube  add  hydrochloric  acid,  as  above, 
and  strong  solution  of  sulphuretted  hydrogen  plentifully: 
— a  yellow  precipitate  is  slowly  formed,  which  is  a  mix- 
ture of  arsenic  trisulphide  and  sulphur,  according  to  the. 
equation 

2Na2HAs  0,+5H2S=6H20+2Na.O+  As.Sj+S^. 

3.  To  the  third  tube  add  hydrochloric  acid  and  sul- 
phuretted hydrogen  as  in  2,  but  this  time  boil  the  mix- 
ture:— a  yellow  precipitate,  arsenic  pentasulphide,  AS2S5,  is 
formed,  according  to  the  equation 

2Na2H  As  0,+oH2S=6H20+2Na,0+  As^Sj. 
Let  the  precipitate  settle,  decant,  and  treat  the  precipitate 
with  ammonium  sulphide,  and  it  is  dissolved, 

4.  Take  the  reaction  of  the  liquid  in  the  4th  tube: — it 
is  alkaline.  Add  cupric  sulphate  solution,  drop  by  drop; 
at  first  a  white  precipitate  is  formed  which  becomes 
slightly  greenish  as  more  of  the  copper  salt  is  added. 
Add  the  cupric  sulphate  solution  plentifully,  and  the  pre- 
cipitate is  dissolved. 

5.  Take  the  reaction  of  the  liquid  in  the  5th  tube: — 
it  is  alkaline,  add  solution  of  silver  nitrate,  and  a  reddish- 
brown  precipitate  of  silver  arsenate,  AgjAsOi  is  formed. 

6.  To  the  sixth  tube  add  solution  of  ammonium 
molybdate,  and  heat:  a  yellow  precipitate,  ammonium 
arseno-molybdate,  (NH4)3As04. 10M0O3,  is  formed. 

I.  Special  tests  for  both  arsenous  and  ars- 
enic compounds:— 

Heat  Tests. 
I .     Place  a  little  white  arsenic  at  the  bottom  of  a  narrow 
test-tube,  cover  it  with  half  an  inch  or  so  of  dry  charcoal, 


CHEMICAL    ANALYSIS.  461 

and  hold  the  tube  nearly  horizontally  in  the  flame,  cover- 
ing the  mouth  of  the  tube  loosely  with  the  finger.  Let 
the  bottom  of  the  tube  at  first  project  slightly  beyond  the 
flame,  so  that  the  charcoal  may  become  nearly  red-hot; 
then  heat  the  bottom  of  the  tube.  The  arsenic  will  sub- 
lime, and  being  deoxidized  by  the  charcoal  with  formation 
of  carbonic  oxide,  metallic  arsenic,  As,  will  be  deposited 
in  the  cooler  part  of  the  tube,  as  a  dark,  mirror-like  met- 
allic incrustation.  An  odor  of  garlic  is  noticed  during 
the  process. 

2.  If  the  above  test  be  performed  by 
mixing  a  very  little  of  any  dry  arsenical 
compound  with  a  well  made  and  perfectly 
dry  mixture  of  charcoal  and  potassium  car- 
bonate in  the  bulb  of  what  is  known  as  a 
Berzelius  tube,  (fig.  55)  the  arsenic  con- 
Fig.  55.  denses  as  a  metallic  ring  in  the  con- 
stricted part  of  the  tube. 

Reinsch's  Test. 
Make  the  solution  of  arsenous  oxide  described  in  G.  I. 
and  into  it  dip  a  bright  piece  of  thin  copper,  about  a 
quarter  of  an  inch  wide  and  half  an  inch  long.  Heat  the 
solution  and  the  copper  becomes  coated  with  a  dark, 
steel-gray  deposit  of  metallic  arsenic.  Pour  off  the  super- 
natant liquid,  wash,  dry  by  passing  through  flame,  place 
in  the  Berzelius  tube,  and  sublime,  as  in  the  last  reaction. 
The  Marsh  Test  For  Arsenic. 
Generate  hydrogen  in  the  customary  manner,  but  this 
time  in  a  special  apparatus  (fig.  56),  consisting  of  a  flask 
provided  as  usual  with  a  funnel-tube  and  delivery-tube, 
bent  at  right  angles,  the  latter  being  connected  with  a 
wider  tube  filled  with  plugs  of  asbestos;  this  drying  tube 
is  further  connected  with  a  piece  of  hard  glass  tube,  about 
one  foot  long  and  54^  inch  in  diameter,  drawn  out  to  ^  inch 


462  DENTAL    CHEMISTRY. 

in  diameter  at  intervals  of  about  3  inches.  After  the 
hydrogen  has  been  generated,  by  the  action  of  sulphuric 
acid  on  zinc,  apply  a  flame  to  one  of  the  wide  parts  of  the 
glass  tube,  and  heat  for  upwards  of  half  an  hour.  If  the 
materials  used  are  free  from  arsenic 
no  trace  of  a  metallic  mirror  will 
be  found  on  the  constricted  parts 
just  beyond  the  heated  point. 

Now  ignite  the  hydrogen  escaping  from 
the  delivery  tube,  and  note  that  the  flame 
is  almost  colorless.     Next  pour  down  the 
fig-  5&.  thistle  tube  any   solution   containing  ars- 

enic, except  a  sulphide,  and  the  flame  becomes  a  dull, 
livid  blue,  and  emits  a  garlic  odor,  while  above  it  there 
is  seen  a  white  cloud*.  Hold  a  piece  of  cold  porcelain 
to  the  flame,  and  it  becomes  coated  with  a  brown  stain  of 
metallic  arsenic,  the  arseniuretted  (arsenetted)  hydrogen, 
H3  As,  formed  in  the  flask,  being  decomposed  by  the  heat 
of  the  flame,  and  the  arsenic,  in  the  centre  of  the  flame, 
being  in  the  metallic  state,  since  all  the  oxygen  there  is 
taken  up  by  the  hydrogen. 

As  203+12H=2H3As  +3H2O. 

Treat  the  stain  on  porcelain  with  solution  of  bleaching 
powder,  (calcium  hypochlorite)  and  it  readily  dissolves. 
(Solutions  of  compounds  of  antimony  give  the  same  stain, 
but  it  is  insoluble  in  hypochlorite  solutions). 

Further,  hold  a  cold  test-tube  over  the  flame  and  its 
walls  will  be  covered  with  a  white  deposit  of  crystals. 
Examine  them  under  the  microscope,  and  they  will  be 
found  to  be  octahedral. 

Lastly  examine  the  glass  tube  heated,  as  described, 
at  one  of  its  wide  parts,  and  a  blue-black  metallic  mir- 
ror is  seen  at  the  constriction  beyond. 

♦Due  to  formation  of  arsenous  oxide:    2n;iAs+60=As2Hs+3H20. 


chemical  analysis.  463 

Fleitmann's  Test. 

Generate  hydrogen  by  heating  in  the  test-tube  to  near 
the  boiling-point,  a  strong  solution  of  caustic  soda  or 
potash,  and  some  pieces  of  zinc,  according  to  the  equa- 
tion 

Zn-|-2NaHO=H2+Na2Zn02*. 
Now  add  a  drop  of  arsenical  solution,  and  spread  over 
the  mouth  of  the  tube  a  cap  of  filter-paper,  moistened 
with  one  drop  of  solution  of  silver  nitrate.  Again  heat 
the  tube,  taking  care  that  the  liquid  itself  shall  not  spurt 
up  on  the  cap.  A  plug  of  cotton  wool  may  even  be 
placed  in  the  mouth  of  the  test-tube  to  prevent  this 
spurting.  The  arsenic  is  reduced  to  the  metallic  state. 
As,  and  arseniuretted  hydrogen  is  formed,  which,  passing 
up  through  the  cap,  reacts  on  the  silver  nitrate,  giving 
rise  to  the  formation  of  a  purplish-black  spot  (silver). 

H3AS  -h3H,0+6AgN03=H3As  Oj+GHNOa+SAg^. 

This  test  is  of  value  in  distinguishing  arsenic  from 
antimony. 

Arsenic  as  an  impurity  in  acids  or  in  tartar  emetic  and 
other  compounds  may  be  recognized  by 
Bettendorff's  Test. 

To  a  solution  of  stannous  chloride,  in  a  liquid  saturated 
with  hydrochloric  acid  gas,  add  a  very  small  quantity  of 
any  arsenical  solution.  Heat,  and  metallic  arsenic.  As, 
separates,  giving  the  mixture  a  yellowish,  and  then  brown- 
ish hue,  or  a  grayish-brown  turbidity  or  precipitate. 

J.  Compounds  of  Antimony. 

Add  5  grammes  of  antimonous  chloride  to  100 
c.c.  of  water  and  stir  well.  The  solution  is  tur- 
bid from  separation  of  white  oxychloride  of  anit^ 


♦Sodium  zincate. 


464  DENTAL    CHEMISTRY. 

mony,  SbOCl,  powder  of  Algaroth.  Pour  5  c.c. 
of  the  turbid  mixture  into  each  of  seven  test- 
tubes  and  test  as  follows: 

1.  To  the  first  tube  add  hydrochloric  acid  plentifully. 
No  precipitate  is  formed  but  the  liquid  becomes  clear. 

2.  To  the  second  tube  add  HCl  as  before  and  also 
strong  solution  of  sulphuretted  hydrogen  plentifully:  an 
orange-red  precipitate  of  amorphous  antimony  sulphide, 
SbaSg,  is  formed.  Let  settle,  decant,  treat  with  ammonia 
water  and  with  ammonium  sulphide.  The  precipitate  is 
dissolved.  Add  hydrochloric  acid  to  the  solution  and 
re-precipitation  takes  place. 

3.  To  the  third  tube  add  ammonium  sulphide.  The 
same  orange-yellow  precipitate  is  formed. 

4.  To  the  fourth  tube  add  enough  hydrochloric  acid 
to  dissolve  the  precipitate  of  oxychloride  and  to  make  a 
clear  liquid:  then  add  strong  solution  of  sodium  hydrox- 
ide carefully  until  the  acid  is  neutralized,  and  again  a 
white  precipitate  is  formed,  metantimonous  acid, 
HSbOj.  Add  more  sodium  hydroxide  solution  and  the 
precipitate  is  dissolved. 

5.  Repeat  the  above,  using  ammonia  water  and  notice 
that  the  precipitate  is  not  dissolved  in  excess  of  ammonia, 

6.  Into  the  sixth  tube  drop  a  piece  of  copper  foil,  and 
boil,  A  black  deposit  of  antimony  is  formed  on  the  cop- 
per. Remove  the  copper,  and  heat  in  the  Berzelius  tube: 
the  antimony  is  volatilized,  and  deposits  as  a  white  crust, 
SbjOa,  on  the  glass. 

7.  Pour  a  few  drops  of  the  contents  of  the  seventh 
tube  into  the  Marsh  apparatus,  and  test  as  for  arsenic: 
the   stain  is  insoluble  in  hypochlorite. 

Now  make  a  solution  of  four  grammes  of  tartar  emetic, 
2KSbO.C4H406,  in  100  c.c.  of  water.  Pour  into  seven  tubes 
and  test  as  above. 


CHEMICAL   ANALYSIS.  465 

I.  Note: — To  the  first  tube  add  a  few  drops  only  of 
hydrochloric  acid:  a  white  precipitate,  antimony  oxy- 
chloride,  is  formed;  add  5  c.c.  of  acid,  shake,  and  the  pre- 
cipitate is  dissolved. 

In  the  fourth  and  fifth  tubes  no  hydrochloric  acid  will 
be  necessary. 

K.  Stannous  Compounds. 

Add  5  grammes  of  stannous  chloride  to  100 
c.c.  of  water.  A  turbid  mixture  results.  Pour 
5  c.c.  of  it  into  each  of  four  test-tubes  and  pro- 
ceed as  follows:— 

1.  To  the  first  tube  add  hydrochloric  acid  plentifully. 
Some  turbidity  still  remains. 

2.  To  the  second  tube  add  strong  solution  of  sulph- 
uretted hydrogen  plentifully:  a  dark-brown  precipitate, 
stannous  sulphide,  SnS,  is  formed: — 

SnCl2-|-H,S=2HCl-l-SnS. 
Let  precipitate  settle,  decant,  treat  with   ammonia    water 
and  warm  (not  boiling)  ammonium  sulphide;  the   preci- 
pitate is  dissolved. 

3.  To  the  third  tube  add  a  few  drops  of  ammonium 
sulphide: — the  same  precipitate  is  formed  as  in  2. 

4.  To  the  fourth  tube  add  strong  solution  of  sodium 
hydroxide  in  small  quantity;  an  abundant  white  preci- 
pitate, stannous' hydroxide,  Sn(HO)2,  is  formed.  Add 
slight  excess  of  the  sodium  hydroxide  solution,  shake, 
and  the  precipitate  is  dissolved  leaving,  however,  a 
slightly  turbid  solution  as  before.  Now  boil  and  a 
flocculent  precipitate,  SnO,  separates.  Let  stand  and  it 
will  soon  be  seen  to  be  of  dark  color. 

In  order  that  this  last  experiment  shall  succeed,  as  above 
described,  use  small  quantities  of  sodium  hydroxide  solu- 
tion both  to  precipitate  and  to  dissolve. 


466 


DENTAL    CHEMISTRY. 


L.  Stannic  Compounds. 

Make  a  solution  of  5  grammes  of  stannic  chlor- 
ide in  100  c.c.  of  water.  Notice  that  the  turbid- 
ity seen  in  K  is  absent.  Pour  5  c.c.  of  the  solu- 
tion into  each  of  four  test-tubes  and  test  as  fol- 
lows: 

1/  To  the  first  tube  add  hydrochloric  acid  plentifully. 
No  precipitate  is  formed. 

2.  To  the  second  add  solution  of  sulphuretted  hydro- 
gen plentifully: — a  yellow  precipitate,  stannic  sulphide, 
SnSa,  is  formed.  Let  settle,  decant,  treat  precipitate 
with  ammonia-water  to  neutralize  acid,  and  add  ammon- 
ium sulphide;  it  is  dissolved. 

Dilute  the  solution  in  ammonium  sulphide  with  water 
and  add  hydrochloric  acid.  The  sulphide  is  reprecipitated. 

3.  To  the  third  tube  add  water,  till  half  full,  then  a 
few  drops  of  ammonium  sulphide,  and  the  same  precipi- 
tate as  in  2  is  formed. 

4.  To  the  fourth  tube  add  solution  of  sodium  or  pot- 
assium hydroxide;  a  white  precipitate  is  formed,  stannic 
acid,  HaSnOj.  Dissolve  the  precipitate  by  adding  excess 
oidAkdiW,  filter,  if  ?iecessary,  dind  boil.  No  reprecipitation 
takes  place.    (Differentiation  from  stannous  compounds.) 

M.  Compounds  of  Gold:— 

Make  a  solution  of  1  gramme  of  auric  chloride, 
AUCI3,  in  20  c.c.  of  water.  Pour  5  c.c.  of  it  into 
each  of  four  test-tubes  and  test  as  follows:— 

1.  Add  hydrochloric  acid  to  the  first  tube.  No  precip- 
itate is  formed. 

2.  To  the  second  tube  add  strong  solution  of  sulph- 
uretted hydrogen  plentifully:  a  brown  precipitate,  auric 
sulphide,  AugSg,  is  formed: — 

2AuCl3+3H2S=Au2S3+6HCl 


CHEMICAL   ANALYSIS.  467 

Let  settle,  decant,  and  treat  precipitate  with  yellow  am- 
monium sulphide.     It  is  dissolved. 

3.  To  the  third  tube  add  solution  of  ferrous  sulphate, 
and  set  aside  for  a  few  hours;  metallic  gold  is  precipitated 
as  a  dark  powder.  Filter  the  solution,  wash  from  the 
filter  paper,  let  settle,  decant,  boil  with  hydrochloric  acid, 
let  settle  again,  filter,  wash,  and  dry.  Mix  with  equal 
weight  of  borax,  and  fuse  in  a  furnace.  A  button  of  met- 
allic gold  is  obtained. 

Note: — Gold  residues  of  laboratory  operations  may  be 
worked  up  in  this  way,  by  dissolving  the  fragments  in 
aqua  regia,  which  is  a  mixture  of  3  parts  nitric  acid  with 
4  of  hydrochloric,  evaporating  nearly  to  dryness,  and 
diluting  with  water. 

Read  paragraph  252  for  further  tests.  For  the  purple 
of  Cassius  test  see  paragraph  258. 

4.  In  the  solution  in  the  fourth  tube  immerse  a  piece 
of  tin-foil.     Purple  of  Cassius  is  formed  and  deposits. 

N.  Compounds  of  Platinum:— 

Dissolve  1  gramme  of  pure  platinic  chloride  in 
20  c.c.  of  water.  Into  each  of  four  test-tubes 
pour  5  c.c.  of  the  solution  and  test  as  follows: — 

1.  To  the  first  tube  add  hydrochloric  acid.  No  preci- 
pitate is   formed. 

2.  To  the  second  tube  add  5  c.c.  of  a  solution  of  sod- 
ium chloride,  and  a  strong  solution  of  sulphuretted  hydro- 
gen plentifully.  A  dark-brown  precipitate,  platinic  sul- 
phide, PtS2,  is  formed.  Filter,  wash,  add  ammonium 
sulphide,  and  the  precipitate  is  dissolved. 

3.  To  the  fourth  tube  add  excess  of  sodium  carbonate 
and  sugar.  Boil.  A  black  precipitate  (metallic  platinum) 
is  formed. 

4.  To  the    fifth  tube  add  solution  of  ammonium  chlo- 


468  DENTAL   CHEMISTRY. 

ride:  a  yellow,  granular  precipitate,  double  chloride  of 
ammonium  and  platinum,  PtCl4.2NH4Cl,  is  formed.  Let 
settle,  decant,  collect  on  a  filter,  wash,  dry,  and  heat  in  a 
small  crucible.  The  precipitate  is  decomposed,  and  the 
metal  remains  as  a  finely  divided  gray  powder  (spongy 
platinum): — 

3(PtCl,.2NH,Cl)=Pt3+2NH,Cl+16HCl+2N2 

548.  0.  Ferrous  Compounds. 

Dissolve  5  grammes  of  ferrous  sulphate  in  lOQ 
ex.  of  water.  Pour  5  c.c.  of  this  solution  into 
each  of  five  test-tubes  and  test  as  follows:— 

1.  Add  hydrochloric  acid  to  the  first  test-tube:  no 
precipitate  is  formed. 

2.  To  the  second  test-tube  add  a  few  drops  of  hydro- 
chloric acid,  and  strong  solution  of  sulphuretted  hydrogen 
plentifully.     No  precipitate  is  formed. 

3.  To  the  third  test-tube  add  a  few  drops  of  ammonium 
sulphide.    A  black  precipitate,  FeS,  is  formed: 

FeSO,+2NH,HS=FeS-f-(NH,),SO,+R,S 
Further  add  a  little  hydrochloric  acid,  and  the  black  pre- 
cipitate dissolves,  with  effervescence   and   separation   of 
sulphur. 

4.  To  the  fourth  tube  add  solution  of  potassium  fer- 
rocyanide:  a  whitish  precipitate  is  formed,  soon  turning 
blue,  KjFeFeCye. 

5.  To  the  fifth  tube  add  solution  of  potassium  ferricy- 
anide;ablue  precipitate,  ferrous  ferrocyanide,is  formed 
FegFejCyia. 

P.  Ferric  Chloride. 

Dissolve  5  grammes  of  ferric  chloride  in  1 00 
c.c.  of  water.  Pour  5  c.  c.  into  each  of  five  test- 
tubes  and  test  as  follows:— 


CHEMICAL    ANALYSIS.  469 

1.  To  the  first  tube  add  hydrochloric  acid;  no  preci- 
pitate is  formed. 

2.  To  the  second  tube  add  a  few  drops  of  hydrochlo  - 
ric  acid  and  plenty  of  strong  solution  of  sulphuretted 
hydrogen:  a  turbid  liquid  results  with  deposition  of  sul- 
phur, and  reduction  of  the  ferric  salt: — 

Fe,CU+H3=2FeCl+2HClH-S 

3.  To  the  third  tube  add  ammonium  sulphide  (half  a 
dozen  drops): black  ferrous  sulphide,  FeS.is  precipitated. 

4.  To  the  fourth  tube  add  solution  of  potassium  fer- 
rocyanide.  A  dark  blue  precipitate  is  formed,  ferric 
ferrocyanide,  Prussian  blue: 

2Fe,Cl«+3(K,FeCye)=12KCl+Fe,3(FeCye) 

5.  To  the  fifth  tube  add  solution  of  potassium  sulpho- 
cyanate;  a  blood-red  orecipitate  is  formed,  ferric  sulpho- 
cyanate. 

Q.  Compounds  of  Manganese:— 

Dissolve  5  grammes  of  manganese  sulphate, 
MnSO^,  in  100  ex.  of  water.  Pour  5  c.c.  of  this 
solution  into  each  of  three  test-tubes  and  test 
as  follows:— 

1.  To  the  first  add  hydrochloric  acid;  no  precipitate 
is  formed. 

2.  To  the  second  add  a  few  drops  of  hydrochloric 
acid,  and  strong  solution  of  sulphuretted  hydrogen, 
plentifully:  no  precipitate  is  formed. 

3.  To  the  third  tube  add  a  few  drops  of  ammonium 
sulphide:  a  yellowish-pink,  or  flesh  colored  precipitate  of 
hydrous  manganese  sulphide,  MnS.HjO,  is  formed: — 

MnS0,+  (NH,)2S     (NH,)2S0,-|-MnS 
Let  the  precipitate  settle,    decant,  treat  the    precipitate 
with  acid,  and  it  is  dissolved. 


470  DENTAL    CHEMISTRY. 

R.  Compounds  of  Chromium. 

Dissolve  5  grammes  of  chromic  chloride  in 
100  c.c.  of  water.  Pour  5  c.c.  of  this  solution 
into  each  of  four  test-tubes  and  test  as  follows:— 

1.  To  the  first  tube  add  hydrochloric  acid.  No  pre- 
cipitate is  formed. 

2.  To  the  second  tube  add  a  few  drops  of  hydrochloric 
acid,  and  plenty  of  strong  solution  of  sulphuretted  hydro- 
gen.    No  precipitate  is  formed. 

3.  To  the  third  tube  add  ammonium  sulphide;  a  gray- 
green  precipitate  is  formed,  chromic   hydrate,   Cr.(H0)6: 

Gr2Cl6+3[(NH,)2S]+6H,0-6NH,Cl+3H,S-hCr2(HO)6 

4.  To  the  fourth  tube  add  a  few  drops  of  sodium  hydrox- 
ide solution:  the  green  hydroxide  is  precipitated,  and  is 
soluble  with  green  color  in  excess  of  the  hydroxide. 
Boil  and  there  is  reprecipitation. 

S.  Compounds  of  Zinc:— 

Dissolve  5  grammes  of  zinc  sulphate  in  100 
c.c.  of  water.  Pour  5  c.c.  of  this  solution  into 
each  of  five  test-tubes  and  test  as  follows:— 

1.  To  the  first  tube  add  hydrochloric  acid.  No  pre- 
cipitate is  formed. 

2.  To  the  second  tube  add  hydrochloric  acid  and 
solution  of  sulphuretted  hydrogen  plentifully;  no  preci- 
pitate is  formed. 

3.  To  the  third  tube  add  half  a  dozen  drops  of  ammo- 
nium sulphide;  a  white  precipitate  is  formed,  zinc  sulph- 
ide, ZnS: — 

ZnSO,+(NH,)2S     (NH,)2SO,+ZnS. 
The  sulphide  is  greenish  or  dark  colored,  if  the   zinc  sul- 
phate contains  iron  or  lead  as  impurities.     Let  the   pre- 
cipitate settle,  decant,  and  treat  precipitate   with    hydro- 


CHEMICAL  ANALYSIS.  471 

chloric    acid,  and   it  dissolves,  a    turbid   liquid     resulting 
(separation  of  sulphur). 

4.  To  the  fourth  test-tube  add  ammonia-water  cau- 
tiously, letting  it  trickle  down  the  side  of  the  tube;  a 
white  precipitate  is  formed,  zinc  hydrate,  Zn2HO.  Add 
the  ammonium  hydroxide  solution  freely,  and  the  preci. 
pitate  is  dissolved. 

5.  To  thefifth  tube  add  solution  of  potassium  ferrocyan- 
ide;  a  whitish  precipitate,  zinc  ferrocyanide,  ZnjFeCye  is 
formed. 

T.  Compounds  of  Aluminium. 

Dissolve  5  grammes  of  aluminium  chloride 
or  sulphate  in  100  ex.  of  water.  Pour  5  c.c. 
of  this  solution  into  each  of  six  test-tubes  and 
test  as  follows: — 

1.  To  the  first  tube  add  hydrochloric  acid;  no  preci- 
pitate is  formed. 

2.  To  the  second  tube  add  a  few  drops  of  hydrochloric 
acid,  and  plenty  of  strong  solution  of  sulphuretted  hydro- 
gen: no  precipitate  is  formed. 

3.  To  the  third  tube  add  ammonium  sulphide;  a  gel- 
atinous, white  precipitate  is  formed,  aluminium  hydrox- 
ide, AL(HO),: 

A1,C1«-1-3(NH,).S+6H,0=A1,(H0)6+6NH,C1-|-3H,S 

4.  To  the  fourth  tube  add  ammonia-water  freely:  a 
white  precipitate  of  the  same  hydroxide  is  formed,  insol- 
uble in  excess  of  the  ammonium  hydroxide. 

5.  To  the  fifth  tube  cautiously  add  solution  of  sod- 
ium hydroxide: — the  same  precipitate  is  formed  soluble 
in  excess. 

6.  To  the  sixth  tube  add  potassium  ferrocyanide  solut 
ion:  no  precipitate  is  formed. 


472  DENTAL    CHEMISTRY. 

U.  Compounds  of  Jfickel  and  Cobalt. 

Make  solutions  of  the  respective  sulphates,  5  grammes 
in  100  c.c.  of  water,  and  apply  first  three  tests  fcxr  iron, 
which  are  similar.  Then  (4)  further  add  ammonia-water 
to  each,  and  obtain  incase  of  nickel  a  blue  precipitate, 
cobalt  a  green,  both  soluble  in  excess.  Sodium  or  pot- 
assium hydroxides  give  the  same,  but  insoluble  in  excess. 

V.  Compounds  of  Barium. 

Make  a  solution  of  5  grammes  of  barium 
chloride  in  100  c.c.  of  water.  Pour  5  c.c.  of 
this  solution  into  each  of  seven  test-tubes  and 
test  as  follows  :- 

1.  Hydrochloric  acid:  no  precipitate. 

2.  Hydrochloric  acid  and  sulphuretted  hydrogen:  no 
precipitate. 

3.  Ammonium  sulphide:  no  precipitate. 

4.  Ammonium  hydroxide  (ammonia-water)  together 
with  solution  of  ammonium  chloride  and  carbonate:  a 
white  precipitate,  barium  carbonate,  BaCOj,  is  formed. 

5.  To  the  fifth  tube  add  yellow  potassium  chromate, 
KjCrO^:  a  pale  yellow  precipitate,  barium  chromate, 
BaCrOi  is  formed.  Pour  into  two  test-tubes,  and  add 
acetic  acid  to  one  and  hydrochloric  to  the  other.  The 
latter  only  is  dissolved. 

6.  To  the  sixth  tube  add  sulphuric  acid:  white  barium 
sulphate,  BaS04,  is  immediately  formed.  Let  settle, 
decant,  and  treat  precipitate  with  boiling  nitric  acid.  It 
is  not  dissolved. 

7.  To  the  seventh  tube  add  solution  of  calcium  sulph- 
ate plentifully:  a  white  precipitate  forms  at  once. 

W.  Compounds  of  Calcium. 

Dissolve  5  grammes  of  calcium  chloride  in  100 


CHEMICAL    ANALYSIS.  473 

ex.  of  water.     Pour  5  c.c.  of  this  solution  into 
eacii  of  seven  test-tubes  and  test  as  follows: — 

1.  Hydrocliloric  acid:  no  precipitate. 

2.  Hydrochloric  acid  and  sulphuretted  hydrogen:  no 
precipitate. 

3.  Ammonium  sulphide:  no  precipitate. 

4.  Ammonium  hydroxide,  chloride,  and  carbonate:  a 
white  precipitate  is  formed,  calcium  carbonate,  CaCOj: — 

CaCl2+(NH,)2C03=CaC03+2(NH,)CI 

5.  To  the  fifth  tube  add  sulphuric  acid:  no  precipitate. 

6.  To  the  sixth  tube  add  potassium  chromate  solution: 
no  precipitate  is  formed. 

7.  To  the  seventh  tube  add  ammonium  oxalate  solution: 
white  precipitate,  calcium  oxalate,  CaCaO^;  pour  the  pre- 
cipitate into  two  test-tubes;  to  one  add  acetic  acid,  to  the 
other  hydfochloric.      The  latter  only  is  dissolved. 

Show  the  presence  of  calcium  in  teeth  by  dissolving  in 
hydrochloric  acid.  Filter,  expel  acid  by  evaporation, 
dissolve  residue  in  water;  add  excess  of  ammonia,  dissolve 
precipitate  with  the  smallest  quantity  possible  of  acetic 
acid,  and  add  solution  of  ammonium  oxalate. 

X.  Compounds  of  Strontium. 

Dissolve  5  grammes  of  strontium  nitrate  in 
100  c.c.  of  water.  Pour  the  solution  into  each 
of  seven  test-tubes  and  test  as  for  barium. 

The  reactions  are  the  same  except  that  calcium  sul- 
phate gives  a  white  precipitate  forming  slowly. 

Y.  Compounds  of  Magnesium. 

Make  a  solution  of  5  grammes  of  magnesium 
sulphate  in  100  c.c.  of  water.  Pour  5  c.c.  of 
this  solution  into  each  of  five  test-tubes  and  test 
as  follows: — 


474  DENTAL    CHEMISTRY. 

1.  Hydrochloric  acid:  no  precipitate. 

2.  Hydrochloric  acid  and  sulphuretted  hydrogen:  no- 
precipitate. 

3.  Ammonium  sulphide:  no  precipitate. 

4.  Ammonium  chloride,  hydrate,  and  carbonate:  no 
precipitate. 

5.  To  the  fifth  tube  add  ammonia-water  and  solution 
of  sodium  hydro-phosphate: — a  crystalline  precipitate  of 
ammonium-magnesium  phosphate,  Mg(NH4)P04+6Aq., 
is  produced,  insoluble  in  ammonia-water  but  soluble  in 
acids,  even  in  acetic  acid. 

Z.  Compounds  of  Ammonium,  Sodium, 
and  Potassium:— 

Dissolve  5  grammes  of  ammonium  chloride  in 
100  ex.  of  water,  and  pour  into  nine  test-tubes. 
Test  as  follows: —  no  precipitate  with  any  of  the 
reagents  used  up  to  Z. 

6.  Into  the  sixth  tube  pour  a  little  of  solution  of  sod- 
ium hydroxide  and  boil:  odor  of  ammonia  is  distinctly 
recognized. 

7.  Test  with  platinic  chloride  as  in  case  of  Potassium, 
which  see. 

8.  Test  with  sodium  cobaltic  nitrite  as  with  Potassium, 
which  see. 

g.  To  the  ninth  tube  add  water,  till  it  is  nearly  full,. 
then  a  little  Nessler's  solution  (potassio-mercuric  iodide) 
and  a  reddish-brown  precipitate  is  formed. 

10.  Finally  heat  some  of  the  dry  compound  on  plat- 
inum foil:  it  volatilizes  at  low  red  heat. 

Make  a  solution  of  sodium  chloride,  5  grammes 
to  100  c.c.  of  water.  Pour  5  c.c.  into  each  of 
five  test-tubes,  and  test  as  follows. 

I.     No  precipitate  with  hydrochloric  acid, sulphuretted. 


CHEMICAL    ANALYSIS.  475 

hydrogen,  ammonium  sulphide,  ammonium  chloride,  hy- 
droxide, and  carbonate,  or  sodium  hydro-phosphate. 

2.  Sodium  compounds  are  white. 

3.  Heat  the  dry  salt  on  platinum  foil.  It  is  not  vol- 
atilized below  red  heat. 

4.  Dip  the  looped  end  of  a  platinum  wire  into  the 
solution,  made  as  first  directed,  and  introduce  the  loop 
into  the  lower  part  of  an  alcohol-lamp  flame,  or  other 
colorless  flame.  An  intense,  brilliant,  luminous,  yellow 
color  is  imparted  to  the  flame. 

Potassium. 
Dissolve  5  grammes  of  potassium  nitrate  in  lOO  c.c.  of 
water,  pour  5  c.c.  of  the  solution  into  each  of  eight   test- 
tubes  and  test  as  follows: — 

1.  No  precipitate  with  the  usual  group  reagents. 

2.  To  5  c.c.  of  a  potassium  chloride  or  nitrate  solution 
in  a  test-tube  add  a  few  drops  of  hydrochloric  acid,  then 
solution  of  platinic  chloride  and  alcohol.  Stir  the  mix- 
ture with  a  glass  rod:  a  yellow  granular  or  slightly  crys- 
talline precipitate  slowly  forms,  PtCl4(KCl)2: 

2KCl+PtCl4=PtCU(KCl)2; 

or 

2KN03+2HCl+PtCl,-=PtCl,(KCl)2+2HN03 

3.  To  5  c.c.  of  solution  of  a  compound  of  potassium 
add  solution  of  sodium  cobaltic  nitrite:  a  yellow  preci- 
pitate, potassium  cobaltic  nitrite  (KN02)6.Co^(N02)g 
-f-HjO   is  formed,  in  neutral  or   slightly   acid    solutions. 

4.  Make  a  saturated  solution  of  any  potassium  com- 
pound, take  the  reaction  and  neutralize,  if  necessary. 
Then  add  freshly  prepared,  strong  solution  of  tartaric 
acid;  a  white  precipitate,  potassium  acid  tartrate,  KHC4 
H^Og,  is  slowly  formed.  Add  alcohol  and  the  precipi- 
tate forms  more  rapidly. 

c;.     Perform  the  flame  test  as  with  sodium,  and    look  at 


476  DENTAL    CHEMISTRY, 

the  flame  through  a  thin  vessel  filled  with  indigo  solution. 
A  violet  color  appears. 

6.  Compounds  of  potassium  are  white,  except  the 
chromate,  dichromate,  permanganate,  etc.,  are  soluble,  and 
not  volatile  at  low  red  heat. 


CHEMICAL    ANALYSIS.  477 


CHAPTER  X. 

APPLICATION    OF    CHEMISTRY    TO    DENTISTRY. 

549.  Short  scheme  for  qualitative  analysis 
of  ordinary  metals.— 

I.  Add  hydrochloric  acid:  a  precipitate 
may  be: 

Silver  chloride,  ] 

Mercurous  chloride,  V  White. 
Lead  chloride,  ) 

'  Add  ammonia  abundantly  to  all  three  pre- 
cipitates and  shake  well:  silver  is  dissolved,  a 
mercurous  compound  blackened,  lead  not  dis- 
solved nor  blackened. 

II.  If  nothing  with  HCl,  add  hydric  sul- 
phide: a  precipitate  maybe: 

Insoluble  in  ammonium  sulphide.     Soluble  in  ammonium  sulphide. 

Mercuric  sulphide.    )  ^  Arsenous  sulphide,  yellow. 

Bismuth  sulphide.     >  ^  Antimonoussulphide, orange. 

Cupric  sulphide.        )  2  Stannous  sulphide,  brown. 

Cadmium  sulphide,  yellow.  Stannic  sulphide,  yellow. 

Auric  sulphide,  brown. 

Platinic  sulphide,  brown. 

A.  In  order  to  ascertain  whether  the  precipitate  is 
soluble  or  not  in  ammonium  sulphide,  throw  on  a  filter, 
wash  well,  wash  off  precipitate  from  filter,  by  means  of 
wash  bottle,  into  a  porcelain  dish,  let  settle,  pour  off 
supernatant  liquid,  then  add  ammonium  sulphide  and 
stir  well.  If  insoluble  in  ammonium  sulphide,  the  original 
solution  contained  either  lead,  mercury(-ic),  bismuth,  cop- 
per, or   cadmium.     Cadmium  is   easily  told  by  its  yellow 


478  DENTAL   CHEMISTRY. 

color,  a  mercuric  salt  by  the  change  of  color,  on  addition 
of  hydric  sulphide  (reddish-yellow  to  black,  with  a  mot- 
tled appearance).  If  neither  of  these  be  found,  take  a 
fresh  amount  of  the  original  solution,  and  add  ammonium 
hydrate:  if  it  is  copper,  a  beautiful  blue  color  is  seen  at 
once.  If  none  of  the  above  tests  are  successful,  it  is 
probably  bismuth,  or  a  dilute  solution  of  lead.  To  a 
fresh  amount  of  the  original  solution,  add  potassium 
chromate:  a  bright  yellow  precipitate  indicates  lead. 
{^Dilute  solutions  of  lead  may  not  be  precipitated  by 
hydrochloric  acid,  but  yet  may  yield  a  slight  precipitate 
of  a  dark  color  with  hydric  sulphide,  verified  by  potas- 
sium chromate).  If  no  lead  be  found,  take  a  fresh 
amount  of  the  original  solution,  and  add  hydric  sulphide.' 
A  black  precipitate,  insoluble  in  dilute  hydrochloric  acid, 
indicates  bismuth. 

B.  If  the  precipitate  is  soluble  in  ammonium  sulphide, 
the  color  of  the  precipitate  produced  by  addition  of 
hydric  sulphide  will  serve  to  distinguish  antimony,  which 
yields  an  orange  precipitate  in  an  acid  solution.  Arsenic 
and  tin  (stannic)  yield  yellow  precipitates  with  hydric 
sulphide,  but  the  arsenic  in  acid  solutions  is  distinctly 
lemon-yellow.  If  there  is  any  doubt,  take  some  of  the 
original  solution  and  pour  it  into  an  apparatus  from  which 
hydrogen  is  being  evolved  and  is  burning  at  the  mouth  of 
the  delivery  tube.  If  arsenic  is  present,  the  flame  will 
now  deposit  a  stain  on  cold  porcelain,  soluble  in  sodium 
hypochlorite.  Tin  (stannous),  gold,  and  platinum  form 
brown  precipitates,  when  hydric  sulphide  is  added  to  solu- 
tions of  their  salts.  To  a  fresh  amount  of  the  original 
solution,  add  stannous  chloride:  if  gold  is  present,  a  pur- 
ple color  will  be  seen;  if  platinum,  a  brown;  if  tin,  no 
change. 

III.     If  there  has  been  no  precipitate  with 


CHEMICAL    ANALYSIS.  479 

hydrochloric  acid  and  none  with  hydric  sul- 
phide, take  a  fresh  amount  of  the  original  so- 
lution, add  ammonium  hydrate,  ammonium 
chloride,  and  ammonium  sulphide: 

Ammonium  hydrate  and  sulphide  precipitate 
Iron  group  and  eartlis: 
Ferrous  sulphide,  black. 
Cobaltous  sulphide,  black. 
Nickelous  sulphide,  black. 
Manganous  sulphide,  flesh  colored. 
Zinc  sulphide,  white. 
Chromic  hydrate,  green. 
Aluminium  hydrate,  white. 

If  the  precipitate  produced  by  the  ammon- 
ium sulphide  is  black,  to  a  fresh  amount  of  the 
original  solution  add  potassium  f errocyanide : 
a  blue  precipitate  indicates  presence  of  salt  of 
iyon. 

If  the  precipitate  with  ammonium  sulphide 
is  white  or  greenish-white,  zinc  or  aluminium 
is  the  metal.  Take  a  fresh  amount  of  the 
original  solution,  and  cautiously  add  a  small 
quantity  of  ammonium  hydrate,  causing  it  to 
trickle  down  the  side  of  the  tube:  if  the 
precipitate  formed  is  cleared,  on  addition  of 
plenty  of  ammonium  hydrate,  it  is  zinc,  if  not, 
ahiminittin . 

IV.  If  no  precipitate  has  occurred  in  i,  ii, 
or  III,  take  a  fresh  sample  of  the  original  sol- 


480 


DENTAL    CHEMISTRY. 


ution,  and  add  ammonium  hydrate,  ammonium 
chloride,  and  ammonium  carbonate: 

Ammonium  carbonate  precipitates  Alkaline 
earths: 

Calcium  carbonate,     ] 
Barium  carbonate,       >  White. 
Strontium  carbonate.  ) 

If  ammonium  carbonate  produce  a  white 
precipitate,  add  to  the  original  solution  potas- 
sium chromate:  a  precipitate  of  yellow  color 
indicates  barium,  rather  than  calcium.  If 
there  is  no  precipitate  with  potassium  chro- 
mate, but  a  white  one  with  ammonium  oxalate 
insoluble  in  acetic  acid,  but  soluble  in  nitric,  it 
\scalciuin,  rather  than  barium.  Calcium,  bar- 
ium, and  strontium  are  readily  identified  by 
flame  reactions. 

In  solution  are  left:  alkalies  and  magnes- 
ium: 

Magnesium. 

Potassium. 

Sodium. 

Lithium. 

Ammonium. 
Magnesium  salts  are  recognized  by  yielding- 
a  white  precipitate  with  sodium  phosphate, 
after  addition  of  ammonium  chloride  and 
hydrate:  the  precipitate  is  ammonio-magne- 
sium  phosphate,  readily  soluble  in  acetic  acid. 
Ammonium  salts  do  not  answer  to  any  of 


CHEMICAL    ANALYSIS.  481 

the  preceding  tests,  but,  if  heated  with  potas- 
sium hydrate,  the  odor  of  ammonia  is  notice- 
able and  fumes  are  seen,  if  a  rod,  moistened 
in  hydrochloric  acid,  be  held  at  the  mouth  of 
the  tube. 

Sodium  and  potassium  are  recognized  by 
flame   reaction.    (See  Section  544,  ill). 

Analysis  of  an  Aqueous  or   slightly   acid   solution 
of  ordinary  compounds  of  the  metals. 

Suppose  now  that  the  solution  is  unknown, 
or  contains  compounds  of  several  metals  in  solu- 
tion, it  is  convenient  to  divide  the  metals  into 
groups,  for  purposes  of  analysis,  as  follows: 
Group  1:  Pb,Hg(ous)  and  Ag.  Group  II  (a):Pb, 
Hg(ic),Bi,Cu,Cd;(b)  As,  Sb,Sn,Au,Pt.  Group  III: 
Fe,Co,Ni,Mn,Zn,Cr,Al.  Group  IV:— Ca,Ba,Sr; 
Group  V:—Mg,K,Na,NH,. 

Proceed  with  the  analysis  as  follows: — 

A.  Group  I.  Pb,Ag,Hg:(ous). 

A.  Test  for  metals  of  Group  I  by  adding  hydrochloric 
acid  to  the  solution  to  be  examined.  The  acid  must  be 
chemically  pure  diud  ho.  diddcd  pleyitifidlv-  If  a  precipitate 
is  formed,  filter,  and  save  the  filtrate  (B)  to  examine  for 
metals  of  Group  II.  Wash  well  and  finally  wash  the  preci- 
pitate off  the  filter  into  a  beaker,  boil  with  water,  and  filter 
again,  saving  this  filtrate  (i)  to  test  for  Pb.  Collect  the 
precipitate  not  dissolved  by  the  boiling  water  on  a  filter, 
wash  it  well  on  the  filter,  till  no  longer  acid,  then  add  to 
it,  while   still  on  the   filter,    ammonia-water.     Save  the 


482  DENTAL    CHEMISTRY. 

filtrate  (2)  to  test  for  silver.  If  the  precipitate  on  the 
filter  turns  black  on  addition  of  the  ammonia-water,  Hg 
(ous)  is  present.  Go  back  now  to  filtrate  (i),  and  add 
H2SO4  to  it:  a  white  precipitate  indicates  presence  of 
Pb.  Now  take  filtrate  (2),  and  add  nitric  acid  plentifully 
to  it:  a  white  precipitate  indicates  presence  of  Ag. 

The  beginner  should  mix  the  three  solutions  of  silver, 
lead,  and  mercurous  nitrates  already  made  (Chapter  IX, 
A,  B,  C.)  and  work  out  the  separation  as  above  outlined. 
The  scheme  is  based  on  the  solubility  of  lead  chloride  in 
boiling  water,  the  precipitation  of  compounds  of  lead  by 
sulphuric  acid,  the  blackening  of  mercurous  chloride 
by  ammonium  hydroxide,  the  solubility  of  silver  chloride 
in  ammonium  hydroxide,  and  its  reprecipitation  from  this 
solution  by  nitric  acid.  The  beginner  should  be  required 
to  explain  the  reason  for  every  step  in  the  process. 

B.  Group  II.  Pb,Cd,Cu,Hg(ic)Bi,As,Sb,Sn: 

If  no  precipitate  with  H CI,  pass  H.^S  through  the  acid- 
ulated liquid  for  a  longtime;  or  if  there  has  been  a  pre- 
cipitate whith  HCl,  use  the  filtrate  (B),  obtained  in  A, 
and  pass  a  current  of  H^S  for  a  long  time  into  this. 

If  a  precipitate  forms,  filter  and  save  the  filtrate  (C)  to 
examine  for  metals  of  Group  III.  The  precipitate  will 
contain  one  or  all  of  the  following: — Cd,Cu,Hg,(ic)Pb,  (in 
small  quantity  not  detected  by  HCl)Bi,As,Sb,Sn.  Wash 
the  precipitate  well,  wash  it  off  the  filter-paper  into  a  dish, 
let  settle,  pour  off  supernatant  liquid,  and  add  it  to  filtrate 
(C),  then  add  ammonium  sulphide  freely,  stir  well,  and 
set  it  for  a  time  in  a  warm  place,  at  a  temperature  of 
about  100°  F.  The  object  of  this  proceeding  is  to  separ- 
ate the  sulphides  of  Cd,Cu,Hg(ic).Pb,Bi  from  those  of  As, 
Sb,Sn,  the  latter  being  soluble   in   ammonium  sulphide. 

After  the  precipitate  has  thus  been  digested  in  ammon- 


CHEMICAL   ANALYSIS.  483 

ium  sulphide,  filter  it,  and  save  the  filtrate  (i).  Wash 
the  residue  on  the  filter  thoroughly,  finally  wash  it  off  into 
a  beaker,  let  settle,  pour  off  supernatant  liquid,  add 
HNO3,  ^^<^  t)oil.  The  object  of  this  procedure  is  to  sep- 
arate mercuric  sulphide  from  the  sulphides  of  Cd,Cu,Pb, 
and  Bi  which  are  all  soluble  in  strong  boiling  nitric  acid. 
If  after  boiling  in  nitric  acid  an  insoluble  residue  remains, 
presence  of  Hg(ic)  is  indicated,  and  the  original  solution 
will  deposit  mercury  on  a  strip  of  copper.  (It  is  often 
the  case  that  a  yellow  half  fused  globule  of  sulphur  re- 
mains after  boiling  with  nitric  acid.  The  color  and  fusi- 
bility of  this  residue  indicates  its  constitution.  In  case  it 
is  not  yellow  or  if  there  is  doubt,  dissolve  in  aqua  regia, 
concentrate  by  evaporation,  dilute  with  water,  and  test 
for  Hg(ic)  with  KL).  After  boiling  with  nitric  acid, 
filter,  and  filtrate  (2)  will  contain,  Cd,Cu,Pb,  and  Bi,  if 
present.  Add  to  this  filtrate  a  few  drops  of  dilute  sul- 
phuric acid.  A  white  precipitate  indicates  presence  of 
lead,  now  in  form  of  sulphate.  Filter,  and  save  the  fil- 
trate (3).  Wash  the  white  precipitate  on  the  filter  till  free 
from  acid,  finally  wash  from  the  filter  into  a  test-tube  or 
beaker,  add  solution  of  ammonium  tartrate  and  excess  of 
ammonium  hydroxide,  and  the  lead  sulphate  is  dissolved. 

Now  take  filtrate  (3)  and  supersaturate  it  with  strong 
ammonia-water.  A  white  precipitate  indicates  presence 
of  bisjmith,  now  in  form  of  hydroxide;  filter,  save  filtrate  (4), 
wash  precipitate  from  the  filter,  let  settle,  decant,  dissolve 
precipitate  in  HCl,  and  test  for  bismuth  as  in  Chapter 
IX,  F.  Next  take  filtrate  (4)  and  test  it  for  Cu  and  Cd: — 
add  solution  of  potassium  cyanide  and  hydric  sulphide. 
A  yellow  precipitate  indicates  Cd.  Filter  and  the  filtrate 
(5)  will  contain  Cu.  Render  the  solution  acid,  and  test 
with  potassium  ferrocyanide,  as  in  Chapter  IX.  E. 

Now  go  back  to  filtrate  (i)  of  this   group  which  con- 


484  DENTAL    CHEMISTRY. 

tains  As,  Sb,  Sn,  also  perhaps  Au  and  Pt.  Add  dilute 
sulphuric  acid  to  it  drop  by  drop  as  long  as  any  precipi- 
tate is  formed.  The  precipitate  will  consist  of  sulphides 
of  As.Sb.Sn  together  with  sulphur.  Filter,  save  the  fil- 
trate (6),  wash  thoroughly,  finally  wash  precipitate  from 
filter  into  a  beaker,  let  settle,  decant,  add  strong  HCl, 
boil.  Dilute  a  little  after  boiling  and  filter.  Residue  on 
the  filter,  if  yellow*,  is  to  be  tested  for  As  by  boiling  in 
hydrochloric  acid  and  a  little  potassium  chlorate,  and  then 
using  Fleitmann's  test  as  in  Chapter  IX,  I.  Test  the 
filtrate  (6)  for  Sn  and  Sb  by  pouring  into  a  Marsh  appara- 
tus. Sb  escapes  as  HgSb  and  may  be  detected  by  the 
stain  on  the  porcelain  insoluble  in  hypochlorite.  Sn  re- 
mains in  and  with  the  zinc  as  a  black  metallic  powder. 
Collect,  wash,  dissolve  in  HCl  and  test  for  tin  as  in  Chap- 
ter IX,  K. 

C.  Group  III.  Zn,Mii,Co,Ni,Al,Fe,Cr. 

If  no  precipitate  with  either  HCl  or  H.,S,  add  NH^ 
C^NH^HO,  and  NH4HS  to  the  original  solution  or,  if 
there  has  been  a  precipitate,  add  these  reagents  to  the 
filtrate  (C),  obtained  in  B.  A  precipitate  shows  presence 
of  Zn,Mn,Co,Ni,Al,Fe,Cr.  Filter  and  save  the  filtrate 
(D)  to  test  for  metals  of  Group  IV,  wash  the  precipitate 
well,  finally  wash  from  filterinto  beaker,  let  settle,  decant, 
add  very  little  HCl  and  a  few  drops  of  HNO3,  warm, 
boil,  add  NH4HO,  to  supersaturate, stir,  and  filter. 


*A  dark  colored  residue  suggests  special  tests  for  Au  and  Pt. 


CHEMICAL    ANALYSIS. 


485 


Precipitate 

Filtrate. 

Fe    Al    Cr. 

Zn    Mn    Co    Ni. 

Wash,  dry,   fuse  on  foil  with 

Acidify  with  HCoHgO^  pass  H^S, 

NajCO 

.•!  and  KNO:i.  boil  in 

filter. 

water  and  filter. 

Residue 

Filtrate. 

Sol. 

Precipitate. 
Zn    Co    Ni. 

FeoO-i. 

If  yellow.  Cr  pre- 

Mn. 

brown. 

sent.     Divide  in 

-Add 

Boil  with  HCl  and  a  little 

Test 

two  parts. 

NH4HO 

HNO»;  add  KHO,  filter. 

original 

and 

solution 

NH4HS. 

for 
ferrous 

Sol. 
Al 

Sol. 
Cr 

Pink, 
turning 

Fill. 
Zn. 

Precipitate. 
Co    Ni 

or  ferric. 

Add 

Add 

brown. 

Add 

Dissolve  in  HCl, 

NH4CI 

HC..H.,0« 

NH4HS. 

and  proceed  as 

and 

and  excess 

White 

directed 

warm. 

0(  .AgNO^; 

ppt. 

Chapter  V^HI, 

White 

red  ppt. 
Or  boil 

U 

ppt. 

with  H«S04 

and  spirit. 

Green 

solution. 

D.  Group  IV:— Ca,Ba,Sr. 

This  group  is  conveniently  studied  in  connection  with 
Group  V. 

E.  Group  y.  Mg,K,Na,Li,NH,:— 

If  metals  of  Group  I — III  are  absent,  add  to  the  original 
solution  NH^Cl.NH.HO,  and  (NH4).3C03.  Or,  if  they 
are  present,  add  these  reagents  to  the  filtrate  (D)  obtained 
in  C.     Warm  and  filter. 


Precipitate 

Ba    Sr    Ca. 

Collect,  wash,  dissolve  in 

HCoHaOo,  add  excess  of 

K2Cr04.  t.lter. 

Mg 
Add  (N 

Filtrate 
Li    K    Na    NH<. 
H4)2HAs04,  stir,  filter. 

Yellow. 

Filtrate 

Sr    Ca. 

Add  dilute  H0SO4, 

let  stand,  filter. 

White. 

Filtrate 

Li    K    Na    NH^ 

Evaporate  to  small 

bulk.  Add  NH4HO. 

Ppt. 
White. 

Fill. 

Ca. 

Add 

NH.HOand 

{Nrt4)2C204 

White  ppt. 

Ppt.         Filtrate. 
Li.     K    Na    NH4. 

Evaporate, 

ignite, dissolve. 

K  by  PtCU, 

Na  by  flame. 

NH4in  original 

solution. 

486 


DENTAL   CHEMISTRY. 


CHAPTER  XI. 

REACTIONS    OF   ACIDS:    (ACIDULOUS    RADICALS). 

After  having  demonstrated  the  presence  of  a 
compound  of  a  metal  in  a  given  solution 
the  next  thing  in  order  is  to  ascertain  what  acid- 
ulous radical  is  combined  with  it.  Is  the  com- 
pound in  question,  for  example,  a  nitrate,  or  a  sul- 
phate, or  a  chloride  of  the  metal  found?  In  order 
to  answer  this  question  become  familiar  with 
the  following  reactions. 

A.  Carbonates  :~ 

1.  Dissolve  5  grammes  of  sodium  carbonate  in  looc.c. 
of  water.  Add  any  dilute  acid  to  it,  and  effervescence 
takes  place.  Perform  the  experiment  in  a  test-tube  and 
pass  the  gas  formed  into  lime-water: — a  white  precipi- 
tate is  formed. 

2.  Prove  the  presence  of  carbonates  in  the  teeth  by- 
acting  on  the  latter  with  hydrochloric  acid  and  passing 
the  gas  given  off  into  lime-water. 

B.  Sulphides. 

Place  some  sulphide  of  iron  in  small  fragments  in  a 
dish   and  pour  a  little    hydrochloric    acid    on    it: — the 


CHEMICAL    ANALYSIS.  487 

characteristic  odor  of  sulphuretted  hydrogen  is    evolved. 
Soluble  sulphides  blacken  metals,  as  silver. 

C.  Chlorides.  (Hydrochloric  acid). 

Make  a  solution  of  5  grammes  of  sodium  chloride  in 
100  c.c.  of  water.  To  some  of  it  in  a  test-tube  add  solu- 
tion of  silver  nitrate.  A  precipitate  of  silver  chloride  is 
formed.  Examine  it  as  in  Chapter  IX,  A.  [  Now  go  back  to 
mercuric  chloride  Chapter  IX,  D.  and  notice  that  use  of 
ammonia-water  causes  a  precipitate]. 

D.  Bromides.  ( Hydrohromic  acid). 

Make  a  solution  of  5  grammes  of  bromide  of  potassium 

in  100  c.c.  of  water,     i.  Test  as  for    chlorides  with    silver 

nitrate:  a  yellowish-white  precipitate  is  obtained,  insoluble 

in  nitric  acid  and  only  sparingly  soluble  in  dilute  ammonia. 

2.  Add  strong  sulphuric  acid    to    the    dry  bromide  on  a 

plate: — yellowish-red   vapors  of  bromine   are   liberated: 

2KBr+H2S04=2HBr-fNa2S04 

and 

2HBr+H2S04=2Br-fS0  2H-H20 

E.  Iodides. (Hydriodic  acid). 

Dissolve  5  grammes  of  potassium  iodide  in  100  c.c.  of 
water.  Pour  5  c.c.  into  each  of  three  test-tubes  and  test  as 
follows: — ■ 

1.  Pour  into  the  first  tube  solution  of  silver  nitrate 
and  test  further  as  for  bromides. 

2.  To  the  second  tube  add  a  drop  or  two  of  nitric  acid, 
and  some  mucilage  of  starch:  a  dark-blue  color  is  formed. 

3.  To  the  third  tube  add  solution  of  mercuric  chloride; 
a  red  precipitate,  Hgl.^,  is  formed. 

4.  Treat  the  dry  iodide  with  sulphuric  acid;  violet 
vapors  of  iodine  are  evolved. 

F.  Cyanides:— (Hydrocyanic  acid). 

Make  a  solution  of  5  grammes  of  potassium  cyanide    in 


488  DENTAL    CHEMISTRY. 

100  c.c.  of  water.     Pour  5  c.c  of  it  into  eacli  of    three    test 
tubes,   and   test   as  follows:— 

1.  Add  solution  of  silver  nitrate  plentifully  to  the  first 
tube:  a  white  precipitate,  AgCyj  or  AgCN  is  formed:  let 
settle,  decant,  pour  the  precipitate  into  two  test-tubes, 
add  nitric  acid  to  one  and  ammonia  water  to  the  other. 
The  second  is  rather  slowly  dissolved. 

2.  To  the  second  tube  add  a  few  drops  of  solution  of 
ferrous  sulphate  and  a  drop  or  two  of  solution  of  ferric 
chloride;  then  add  solution  of  potassium  hydroxide  and 
finally  hydrochloric  acid.    Prussian  blue  is  formed,  thus: — 

HCN+KHO^KCN+H^O 
2KCN  +  FeS04=Fe(CN).,+K2S04 
4KCN+Fe(CN)2=K4-Fe(CN)5 
3K,Fe(CN)o+2Fe,Cle=12KCl+K,(FeC6N6)3 

G.  Nitrates:— (Nitric  acid.) 

Dissolve  5  grammes  of  potassium  nitrate  in  100  c.c.  of 
water,  and  pour  5  c.c.  of  the  solution  into  each  of  two 
test-tubes. — 

Test  as  follows: — 

1.  To  the  first  tube  add  a  few  small  pieces  of  ferrous 
sulphate,  shake  gently,  then  cause  strong  sulphuric  acid 
(8  or  10  drops  only)  to  trickle  down  the  side  of  the  tube: 
a  reddish  purple  or  black  coloration  will  appear  between 
the  acid  and  supernatant  liquid,  due  to  formation  of 
2FeSO,.NO. 

2.  To  the  second  tube  add  crystals  of  pyrogallic  acid, 
and  test  with  sulphuric  acid  as  above;  a  deep  brown 
color  is  produced  at  the  line  of  contact. 

H.  Clilorates.-- 

1.  Heat  dry  chlorate  of  potassium  and  note  liberation 
of  oxygen. 

2.  To  a  very  little  dry  chlorate  add  a  little  sugar,  mix 
carefully,  then  add  z.few  drops  of  sulphuric  acid.  Action 
takes  place  with  explosive  violence. 


CHEMICAL    ANALYSIS.  489 

I.    Cliromates:—(  Chromic  acid.) 

Chromates  are  easily  recognized  by  the  rich  colors  of 
the  salts;  thus  potassium  chromate  is  bright  yellow,  lead 
chromate  is  so  called  chrome  yellow,  potassium  dichro- 
mate  a  rich  red,  etc. 

Dissolve  5  grammes  of  potassium  chromate  in  lOO  c.c. 
of  water.  Pour  5  c.c.  of  the  solution  into  each  of  five 
test-tubes  and  test  as  follows: 

1,  To  the  first  tube  add  hydrochloric  acid  and 
hydrogen  sulphide  solution:  sulphur  is  precipitated  and 
the  color  turns  green.  The  chromium  is  now  in  the  form 
of  base  instead  of  acid,  sulphate  of  chromium  being  formed. 

2.  Into  the  second,  third,  fourth,  and  fifth  tubes  pour 
solutions  of  compounds  of  lead,  barium,  silver,  and  mer- 
cury (mercurous)  respectively,  and  look  up  the  reactions 
which  take  place  in   Chapter  IX. 

J.    Sulphites:— (Sulpliurous  acid). 

1.  Pour  a  drop  or  two  of  dilute  hydrochloric  acid  on  a 
little  sodium  sulphite  contained  in  a  plate,  and  note  the 
suffocating  odor  of  sulphur  matches,  due  to  formation  of 
H3O3. 

2.  Make  a  solution  of  sodium  sulphite  (5:100)  and 
add  to  it  solution  of  barium  chloride:  a  white  precipitate 
is  formed  soluble  in  dilute  hydrochloric  acid: — 

Na2S03+BaCl2=BaS03+2NaCl 

K.  Sulphates.    (Sulphuric  Acid). 

Dissolve  5  grammes  of  sodium  sulphate  in  100  cc.  of 
water,  and  to  5  c.c.  of  the  solution  add  solution  of  bar- 
ium chloride.  A  white  precipitate  is  formed,  insoluble 
even  in  boiling  nitric  acid,  thus: — 

Na2S04+BaCl2=BaS04+2NaCl 

Commercial  samples  of  hydrochloric  acid  will  give  this 
precipitate  with  barium  chloride,  hence  the  necessity  of 


490  DENTAL    CHEMISTRY. 

using^  chemically  pure  hydrochloric   acid   in   laboratory 
work. 

L.  Phosphates.    (Phosphoric  Acid  . 

Make  a  solution  of  5  grammes  of  sodium  phosphate, 
NajHPO^,  in  iqo  c.c.  of  water.  Pour  5  c.c.  of  it  into  each 
of  three  test-tubes,  and  test  as  follows: — 

1.  To  the  first  tube  add  plentifully  solution  of  am- 
monium molybdate  in  dilute  nitric  acid.  Warm.  A 
yellow  precipitate  is  formed,  ammonium  phospho-moly- 
bdate,  (NH4)3P04.ioMo03.2H20.,  soluble  in  ammonia 
water. 

2.  To  the  second  tube  add  solution  of  barium  chlor- 
ide; a  white  precipitate  of  barium  phosphate  is  formed, 
soluble  in  acids. 

3.  To  the  third  tube  add  solution  of  ferric  chloride: 
a  yellowish-white  precipitate  of  ferric  phosphate,  Fe3 
(P04)2  is  formed: — 

2Na,HPO,+Fe2Cl6     Fe2(P04),+4NaCl+2HCl 
In  practice   a   little  sodium  acetate  is  first   added,  so 
that  liberated  HCl  may  unite  with  the  sodium  and  not 
dissolve  the  precipitate. 

Lastly  dissolve  teeth  in  hydrochloric  acid,  filter,  pre- 
cipitate with  ammonium  hydrate,  filter  again,  wash  pre- 
cipitate from  filter  into  a  dish,  dissolve  in  a  little  dilute 
nitric  acid,  add  ammonium  molybdate  solution  and  heat. 
The  presence  of  phosphates  in  the  teeth  is  thus  proved. 

M.  Borates.  (Boric  Acid). 

Dissolve  5  grammes  of  borax  in  as  little  water  as  pos- 
sible and  pour  into  three  test-tubes. 

I.  Dip  into  the  first  tube  a  piece  of  turmeric  paper:  it 
is  colored  brown-red  as  by  alkalies.  Next  add  a  few 
drops  of  hydrochloric  acid  to  the  borate  solution  and  dip 
a  fresh  slip  of  paper  into  it;  remove,  and  dry  over  a  flame. 
The  brown  color  still  appears. 


CHEMICAL    ANALYSIS.  491 

2.  Into  the  second  tube  pour  solution  of  barium  chlor- 
ide: a  white  precipitate,  barium  metaborate,  Ba2B02,  is 
formed,  soluble  in  acids  and  in  alkaline  salts. 

3.  To  the  third  tube  add  solution  of  silver  nitrate:  a 
white  precipitate  is  formed,  soluble  in  both  nitric  acid 
and  ammonia  water. 

Finally  mix  in  a  dish  some  dry  borax  with  a  few  drops 
of  sulphuric  acid,  and  pour  upon  the  mixture  some  alco- 
hol.    Ignite.     The  flame  is  tinged  greenish  at  its  edges. 

For  convenience  a  number  of  organic  acidulous  radicals 
will  be  included  in  this  chapter. 

^.  Acetates.  (Acetic  Acid). 

Dissolve  5  grammes  of  sodium  acetate  in  about  20  c.c. 
of  water.  Pour  5  c.c.  into  each  of  three  test-tubes.  Test 
as  follows:— 

1.  To  the  first  tube  add  a  few  drops  of  sulphuric  acid 
and  heat:  characteristic  odor  of  vinegar  (acetic  acid)  is 
evolved. 

2.  To  the  second  tube  add  a  little  alcohol,  then  a  few 
drops  of  sulphuric  acid,  and  heat:  a  characteristic  odor 
of  acetic  ether  is  evolved. 

3.  Take  the  reaction  of  the  liquid  in  the  third  tube, 
neutralize  carefully,  if  necessary,  and  then  add  a  few 
drops  of  a  neutral  solution  of  ferric  chloride:  a  deep  red 
liquid  results,  owing  to  formation  of  ferric  acetate, 
FcgS  C2H3O2.  Now  boil  and  a  red  precipitate,  iron  oxy- 
acetate,  occurs  leaving  the  liquid  colorless. 

0.  Oxalates.    (Oxalic  Acid). 

Make  a  solution  of  5  grammes  of  oxalic  acid  or  am- 
monium oxalate  in  100  cc.  of  water.  Pour  5  cc.  into  each 
of  two  test-tubes  and  test  as  follows:— 

I.  To  the  first  tube  add  solution  of  calcium  chloride; 
a  white  precipitate,  calcium  oxalate,  CaCjO^,  is  formed. 
Let  settle,  decant,  and  pour  precipitate  into  two  tubes: 


492  DENTAL    CHEMISTRY. 

add  acetic    acid  to  one  and  hydrochloric  to  the  other. 
The  second  only  is  dissolved. 

2.  To  the  second  tube  add  silver  nitrate:  a  white  pre- 
cipitate is  formed.  Lastly  heat  a  fragment  of  dry  pot- 
assium oxalate  in  a  test  tube;  add  water  and  acid:  effer- 
vescence occurs.  Decomposition  has  taken  place,  carbon 
monoxide  is  driven  off,  and  potassium  carbonate  left: — 
K2C204=K2C03+CO. 

P.  Tartrates.    (Tartaric  Acid). 

Dissolve  i;  grammes  of  potassium  sodium  tartrate  in 
100  cc.  of  water.  Pour  5  cc.  of  this  solution  into  each  of 
three  test-tubes  and  test  as  follows: — 

1.  To  the  first  tube  add  solution  of  calcium  chloride; 
a  white  precipitate,  calcium  tartrate,  CaC4H406  4H  2 O,  is 
formed.  Collect  precipitate  quickly  on  a  filter,  wash, 
and  treat  with  solution  of  potassium  hydroxide.  It  is 
dissolved  on  stirring.  Heat.  Reprecipitation  takes 
place. 

2.  To  the  second  tube  add  acetic  acid  and  solution  of 
potassium  acetate.  Stir  well.  A  crystalline  precipitate, 
acid  potassium  tartrate,  slowly  separates. 

3.  To  the  third  tube  add  solution  of  silver  nitrate, 
first  neutralizing  if  necessary;  a  white  precipitate,  silver 
tartrate,  Ag2C4H406,  is  formed.  Adda  drop  of  ammonia- 
water  and  boil.  It  blackens,  owing  to  reduction,  and 
metallic  silver  forms  as  a  mirror  on  the  tube. 

Short  Scheme  for  Identification  of  Acids  (Acidu- 
lous Radicals). 
A.  If  the  substance  is  in  solid  form,  test  for  a  carbon, 
ate,  sulphide,  bromide,  iodide,  chlorate,  sulphite,  and  bor_ 
ate,  using  dry  tests  as  described  under  the  respective 
headings  in  Chapter  XI.  If  the  acid  is  not  one  of  these 
seven,  dissolve  in  water  in  the  usual  proportions  and  test 
for  a  chloride,  cyanide,  nitrate,  chromate,  sulphate,  phos- 


CHEMICAL    ANALYSIS.  493 

phate,  acetate,  oxalate,  and  tartrate.  Confirm  by  per- 
forming all  the  tests  under  the  heading  of  the  acid  found 
in  Chapter  IX. 

B.  If  the  substance  is  in  liquid  form,  test  for  the  com- 
monest occurring  acidulous  radicals  first:  these  are  the 
chlorides,  nitrates,  and  sulphates.  If  it  is  not  one  of 
these  three,  next  test  for  carbonates,  and  phosphates.  If 
still  it  is  not  found,  test  for  bromides,  iodides,  cyanides, 
chromates,  acetates,  and  oxalates.  Finally  for  sulphides, 
chlorates,  borates,  and  tartrates. 

Hints  on  the  above:  if  silver  is  the  metal,  and  the  sub- 
stance is  in  solution,  do  not  test  for  chlorides;  it  is  likely 
to  be  a  nitrate.  If  lead  is  the  metal,  test  for  nitrate  and 
acetate.  If  a  mercurous  compound  is  found,  first,  test 
for  a  nitrate.  If  copper  is  the  metal,  test  first  for  a  chlor- 
ide, nitrate,  or  sulphate.  If  a  mercuric  compound  is 
found,  test  for  a  chloride  (remembering  the  peculiarity 
of  the  action  of  ammonia-water)  or  for  a  nitrate,  and 
cyanide.  If  bismuth  is  the  metal,  test  for  a  chloride  or  a 
nitrate.  If  arsenic  is  the  metal,  test  for  a  chloride;  if 
found  it  is  probably  a  solution  of  As^Og  in  hydrochloric 
acid;  if  not  found,  test  for  arsenites  and  arsenates  as  in 
chapter  IX.  If  antimony  is  found,  test  for  a  chloride 
and  a  tartrate.  If  tin  is  found,  test  for  a  chloride,  so  also 
if  gold  and  platinum  are  found.  If  iron  is  found,  test  for 
a  chloride,  or  nitrate,  or  sulphate.  If  manganese,  nickel, 
or  cobalt  is  found  test  for  the  same  acids  as  in  case  of 
iron.  If  chromium  is  found,  test  for  a  chloride.  If  zinc 
is  found,  test  for  a  chloride,  or  a  bromide,  nitrate,  or  sul- 
phate. If  aluminium  is  found,  test  for  a  chloride  or  sul- 
phate. If  barium  is  found,  test  for  a  chloride  or  nitrate. 
If  calcium  is  found,  test  for  a  chloride,  strontium  for  a 
chloride  or  nitrate,  magnesium  for  a  chloride,  or  sul- 
phate. If  sodium,  potassium,  or  ammonium  is  found, 
test  first  for  a  chloride,  or  sulphate,  or  nitrate. 


494  DENTAL    CHEMISTRY, 

In  the  author's  experience  as  a  teacher,  oxalic  acid  or 
an  oxalate  is  commonly  mistaken  by  the  beginners  for 
potassium  cyanide.  Oxalic  acid  turns  litmus  bright  red 
while  the  cyanide  solution  turns  red  litmus  blue. 


CHEMICAL    ANALYSIS.  495 


CHAPTER  XII. 

REACTIONS    OF    ORGANIC     SUBSTANCES     OTHER    THAN    ACIDU- 
LOUS   RADICALS.* 

A.  Phenol.    (Carbolic  Acid). 

Read  section  375. 

1.  Substance  is  either  colorless  crystals  or  a  pink 
liquid  having  characteristic  odor.  Note  greasy  stain  on 
paper  and  whitening  of  skin,  with  numbness. 

2.  To  a  few  crystals  or  a  little  of  the  liquid  in  a  test- 
tube  add  very  little  nitric  acid:  violent  action  takes  place 
and  the  solution  turns  yellow,  picric  acid,  C6H2(N02)3 
HO  being  formed. 

3.  Mix  a  few  of  the  crystals  or  a  little  of  the  liquid 
with  half  a  test-tube  full  of  water  and  add  a  few  drops  of 
ferric  chloride  solution:  a  permanent  violet-blue  color  is 
formed. 

B.  Chloroform. 

Read  section  412. 

1.  Note  characteristic  odor  and  hot  sweetish  taste. 

2.  Mix  with  equal  parts  water  and  note  that  it  does 
not  dissolve  but  sinks  to  the  bottom  of  the  tube  in  glob- 
ules. 


♦Organic  acidulous  radicals  have  been  for  convenience  already  considered  in  Chap. 
XL 


496  DENTAL    CHEMISTRY. 

3.  Mix  with  alcohol  and  note  that  it  is  soluble  in  this 
liquid. 

4.  Pour  some  of  it  into  a  dish  and  note  that  it  does 
not  inflame  readily  but  burns  with  a  dull  smoky  flame. 

5.  Dip  a  piece  of  filter  paper  into  it  and  ignite:  the 
paper  burns  with  a  greenish  flame  and  gives  off  fumes  of 
HCl,  recognized  by  clouds  when  a  rod  moistened  with 
ammonia  water  is  brought  near, 

6.  Heat  5  cc,  of  Haines's  solution  to  boiling  and  add 
a  few  drops  of  chloroform.  Note  reduction  as  in  test 
for  Glucose  which  see  in  Chapter  XIV. 

C.    Alcohol. 

Read  section  363. 

1.  Note  odor,  taste,  inflammability,  and  solubility 
in  water. 

2.  Dilute  a  little  alcohol  with  5  cc.  of  water  then  add 
to  it  a  few  drops  of  dilute  KHO  solution  and  a  small 
crystal  of  iodine.  A  precipitate,  iodoform,  of  character- 
istic odor  is  formed,  according  to  the  equation: — 

QH,HO+6KHO+Is=CHl3+CHO,K+5KI+5H,0 
If  too  much  alcohol  is  present,  the  precipitate  is  dis- 
solved. 

D.  Glycerol.  (Glycerin). 

Read  section  369. 

1.  Note  the  thick  syrupy  consistence,  sweet  taste, 
solubility  in  water  and  alcohol,  and  absence  of  inflamma- 
bility. 

2.  Warm  a  solution  of  glycerol  in  water  with  a  little 
sulphuric  acid  and  note  odor  of  acroleim, 

3.  Note  no  reduction  of  Haines's  test  liquid. 

E.  Etlier.  (Sulphuric  Ether). 

Read  section  400. 

I,  Note  odor,  volatility,  and  great  inflammability:  the 
latter  is  well  shown  by  pouring  some  ether  into  a  dish 


CHEMICAL    ANALYSIS.  497 

and  approaching  it  with  a  long  lighted  taper.  The  ether 
takes  fire  before  the  flame  touches  it,  owing  to  ignition  of 
the  vapor  all  about  the  dish. 

F.  Alkaloids: 

For  identification  of  alkaloids  (section  449)  as 
distinguished  from  other  substances  proceed  as 
follows:— 

1.  Note  {very  caiitiottsly)  the  taste  by  dissolv- 
ing the  substance  in  plenty  of  water  and  tasting 
but  one  drop;  alkaloids  have  bitter  taste. 

2.  Solubility  in  alcohol:  most  alkaloids  and 
their  salts  are  more  or  less  soluble  in  alcohol 
even  though  insoluble  in  water. 

3.  Color:  usually  white. 

4.  Behavior  with  reagents:— aqueous  solu- 
tions of  alkaloids  are  precipitated  by  solutions  of 
KHO  and  NaHO,  and  by  solutions  of  alkaline 
carbonates,  as  Na2C03;  solutions  of  alkaloids  as  a 
class  are  precipitated  by  solutions  of  tannic  acid, 
picric  acid,  phospho-molybdic  acid,  potassio- 
mercuric  iodide,  auric  and  platinic  chlorides. 

VOLATILE   ALKALOIDS. 

I.  Nicotine.  Recognized  by  liquid  state,  brownish 
color  on  exposure  to  air,  strong  odor  of  tobacco,  solu- 
bility in  ether,  chloroform,  turpentine,  water,  and  alcohol 
Precipitated  by  picric  acid,  auric  and  platinic  chlorides, 
and  mercuric  chloride.  Precipitate  by  these  reagents  is 
amorphous,  turning  crystalline.  An  ethereal  solution  of 
iodine  added  to  an  ethereal  solution  of  nicotine  separates 
a  brownish  oil  which  slowly  becomes  crystalline. 

Nicotine  gives  a  violet  color  with  HCl. 


498  DENTAL   CHEMISTRY. 

2.  Coniine.  Recognized  by  liquid  state,  odor  of  mice, 
and  solubility  like  nicotine.  Solutions  are  precipitated 
as  above  by  general  alkaloidal  reagents.  Evaporated 
with  HCl,  a  greenish-blue,  crystalline  residue  is  obtained. 

3.  Sparteine.  Resembles  coniine  and  nicotine  but 
ethereal  iodine  test  separates  dark  greenish-brown  crystal. 

Non-Volatile  Alkaloids. 

Read  section  449. 

As  distinguished  from  the  volatile  alkaloids  they  are 
usually  white  odorless  solids,  fused  at  a  temperature  of 
the  boiling  point  of  water,  but  decomposed  at  higher 
temperatures. 

A.  Morphine  or  its  salts.*  -^ 

1.  To  a  little  of  the  powdered  solid  in  a  plate  add  a 
few  drops  of  nitric  acid:  effervescence  takes  place  and  a 
red  solution  is  formed  which  changes  to  yellow. 

2.  To  a  little  of  the  dry  substance  in  a  dish  add  pure 
H0SO4:  solution  takes  place.  Pour  half  of  the  solution 
into  another  dish.  Add  a  crystal  of  KaCrgO,  to  solution 
in  one  dish,  and  a  small  drop  of  dilute  nitric  acid  to  the 
other:  the  first  turns  green,  the  second  pink. 

3.  Neutralize  a  solution  of  ferric  chloride  with  any 
convenient  alkali  at  hand,  stopping  short  of  actual  pre- 
cipitation: add  this  to  the  substance  and  a  blue  color  is 
developed,  which  changes  to  green  on  addition  of  excess 
of  the  reagent. 

4.  Dissolve  the  substance  in  water  or  other  solvent 
and  note  absence   of  precipitation  with  solution  of  Hg 

5.  Note  precipitation  of  solution  by  saturated  auric  and 
platinic  chlorides,  picric  acid,  and  also  solution  of  potas- 
sium dichromate. 


♦Read  section  459. 


CHEMICAL    ANALYSIS.  499 

B.  Codeine  and  its  Salts. 

1.  Solution  in  nitric  acid  is  yellow. 

2.  Solution  in  chlorine  water  is  colorless,  but  reddened 
by  ammonia  water. 

3.  Solution  in  pure  sulphuric  acid  is  colorless,  but  turns 
blue  when  warmed  with  addition  of  trace  of  ferric  chlor- 
ide. 

C.  Quinine  and  its  Salts. 

Read  section  464. 

1.  Note  insolubility  in  water  by  shaking  up  a  little  of 
the  dry  substance  in  half  a  test-tube  full  of  water.  Next 
add  just  one  drop  of  H^SO^  and  note  how  quickly  solu- 
tion takes  place.  Hold  below  the  window  sill  and  note 
peculiar  blue  fluorescence. 

2.  To  the  solution  thus  made  add  a  few  c.c.  of  chlor- 
ine or  bromine  water  then  excess  of  ammonia  water  and 
note  green  color. 

D.  Caffeine.  (Thein) 

1.  The  solution  in  HNO3  is  yellow.  Evaporate  and 
warm  with  ammonia  water,  and  it  turns  purple. 

2,  The  solution  in  pure  H2SO4  is  colorless. 

E.  Strychnine  and  its  Salts:— 

Read  section  467. 

1.  Add  one  crystal  to  a  quart  of  water  and  note  bitter 
taste. 

2.  Place  a  small  crystal  on  a  plate,  add  one  or  two 
drops  pure  H2SO4,  and  wait  till  it  is  dissolved.  Solution 
is  colorless.  Now  draw  a  small  fragrnent  of  KgCraOy 
through  the  solution,  A  blue  color  I's  developed  which 
rapidly  changes  to  violet,  cherry-red,  and  finally  yellow. 

F.  Brucine. 

I.     The  solution  in  HNO3  is  red  turning  yellow.     Add 


500  DENTAL    CHEMISTRY. 

stannous  chloride  and  the  red  changes  to  violet.    (Differ- 
entiation from  morphine). 

G.  Atropine:— 

Read  section  452. 

1.  The  solution  in  HNO3  is  colorless  and  on  addition 
of  KjCraOy  is  only  very  slowly  colored. 

2.  Add  a  little  HNO3  to  the  dry  substance,  dry  on 
the  water  bath,  cool,  and  add  a  few  drops  of  solution  of 
KHO  in  alcohol;  a  violet  color  is  developed  changing 
slowly  to  red. 

3.  Dissolve  a  fragment  of  KaCr^O,  in  H2SO4,  add  a 
gramme  of  atropine  and  a  few  drops  water,  warm,  and  a 
pleasant  orange  blossom  odor  is  perceived. 

H.  Yeratrine:— 

Read  Section  468. 

1.  The  solution  in  H2SO4  is  first  yellow,  then  orange, 
finally  carmine  red,  and  shows  a  partial  green  fluorescence, 

2.  The  solution  in  HCl  is  colorless  but  turns  dark  red 
when  warmed. 

3.  Addition  of  bromine  water  colors  the  substance 
violet. 

I.  Aconitine; 

Read  section  450. 

1.  The  solution  in  H2SO4  is  yellow  brown. 

2.  The  solution  in  aqueous  phosphoric  acid  when 
evaporated  shows  a  violet  color. 

J.  Pliysostigmine: 

1.  The  solution  in  H2SO4  is  yellow  turning  olive  green. 

2.  The  above,  if  neutralized  carefully  with  ammonia 
water  and  warmed,  turns  red  then  red-yellow,  green,  and 
blue. 

3.  Solution  of  bromine  in  potassium  bromide  turns 
the  substance  red. 


CHEMICAL   AMALYSIS.  501 

K.  Cocaine  and  its  Salts. 

Read  section  457. 

I.     The  solutions  in  H.2SO4  and  HNO3  are  colorless. 

Deportment  of  Alkaloids   with  General  Reagents. 

1.  Picric  acid: — Precipitates  nicotine,  coniine,  spar- 
teine, morphine,  quinine,  strychnine,  brucine,  atropine, 
and  cocaine.     Gives  no  precipitate  with  aconitine. 

2.  Auric  and  platinic  chlorides: — Precipitate  nicotine, 
coniine,  sparteine,  morphine,  atropine,  veratrine,  cocaine. 

3.  Tannic  acid: — Precipitates  quinine,  strychnine, 
brucine,  aconitine. 

4.  Mercuric  chloride: — -Precipitates  nicotine,  coniine, 
sparteine,  strychnine,  cocaine;  does  not  precipitate  acon- 
itine and  morphine. 

5.  Sodium  hydroxide: — Precipitates  quinine,  and  acon- 
itine. 

6.  Iodine  in  potassium  iodide: — Precipitates  strych- 
nine (brown),  veratrine  (brown),  aconitine;  cocaine 
(brown),  dilute  solutions  rose-colored. 


502  DENTAL   CHEMISTRY- 


CHAPTER  Xlll. 

LABORATORY    WORK    CONTINUED — CHEMICAL    WORK    IN    THE 

DENTAL    LABORATORY  :       REFINING   GOLD,    TESTING 

AMALGAMS,    MANIPULATION    OF    VULCANITE, 

COMPOUNDING    RUBBER,    ETC.,  ETC. 

550.  Reftuiiis;  Gold:  the  separation  of  for- 
eign metals  from  gold  is  a  matter  of  great  im- 
portance to  the  dentist,  as  can  be  inferred  from 
page  169,  on  which  the  effects  of  the  different 
metals  on  gold  are  discussed.  Metals  may  be 
separated  from  gold  in  two  ways,  by  the  "dry 
way"  and  the  "wet  way."  The  object  of  the 
"  dry  method,"  or  roasting,  is  to  convert  the 
metals  into  oxides,  chlorides,  or  sulphides. 

1.  Plate-scrap  or  clippings,  and  plate-filings;  these 
need  usually  only  to  be  remelted,  if  of  suitable  fineness 
originally. 

2.  Mixed  filings,  and  fragments  containing  solder  and 
platinum;  these  should  be  either  roasted,  or  reduced  to 
gold  by  the,"  wet  way." 

3.  Sweepings:  these  should  be  first  well  washed,  then 
either  mixed  with  class  second,  or  separately  refined. 

A  good  method  is  to  fuse  8  parts  of  sweepings  with  4  of 


CHEMICAL    WORK    IN    DENTAL    LABORATORY.  503 

common  salt,  4  of  impure  potassium  carbonate,  i  of  potas- 
sium bitartrate,  and  one-half  of  potassium  nitrate,  in  a 
cr-icible. 

551.  Separation  of  foreign  metals  from 
i>'Ol(l:  the  most  troublesome  constituents  of 
g-old  alloys  are  tin,  lead,  zinc,  iron,  antimony, 
bismuth,  etc.,  etc.  Most  of  these  are  oxidiza- 
ble,  hence  roasting-  with  nitre  is  usually  suffi- 
cient, but  tin  alloys  may  better  be  roasted  with 
mercuric  chloride,  and  if  the  alloy  contain  a 
number  of  the  different  metals,  sulphide  of  an- 
timony should  be  used. 

Richardson  recommends  the  following:  meth- 
od : 

1.  Remove  all  traces  of  iron  or  steel  by 
passing-  a  magnet  repeatedly  through  them.* 

2.  Place  the  fragments  and  filings  in  a  clean 
crucible,  lined  on  the  inside  with  borax,  and 
covered  either  with  a  piece  of  fire-clay  slab,  or 
broken  crucible. 

3.  Place  the  crucible  in  a  furnace,  on  a  bed 
composed  of  mixed  charcoal  and  coke. 

4.  Add  small  bits  of  borax  and  when  the 
metallic  mass  is  fluid,  add  the  potassium  nitrate 
(or  whatever  refining  agent  is  used)  in  small 
quantities  from  time  to  time,  and  continue  the 
roasting  from  half  an  hour  to  an  hour,  accord- 
ing to  the  coarseness  of  the  alloy. 

Roasting  with  nitre  is  usually  sufticient,  but 

*Gold  scrap  sometimes  contains  traces  of  steel  that  should  be  re- 
moved by  treatment  in  the  "  wet  way." 


504  DENTAL    CHEMISTRY. 

sometimes  effects  partial  separation  only.     In 
such  a  case  proceed  as  follows  : 

1.  Remove  crucible  from  the  fire,  after 
roasting"  with  nitre,  and  let  cool  gradually. 

2.  Break  the  crucible,  remove  the  button  of 
g"old,  separate  from  slag;  by  use  of  hammer, 
put  into  a  new  crucible,  and  melt  again. 

3.  Add  any  particular  agent  capable  of 
uniting  with  any  particular  base  metal  known 
to  be  present;  or,  try,  first,  one  refining'  agent 
then  another,  until  sufficient  separation  is 
effected. 

4.  Pour  the  melted  metals  into  previously 
warmed  and  slightly  oiled  ingot  moulds. 

5.  Hammer,  anneal,  and  roll  the  ingot,  and 
if  still  brittle,  melt  again  with  mercuric  chlor- 
ide. 

Another  method,  of  advantage  in  a  greatly 
impoverished  alloy,  is  the  following;: 

1.  Melt  the  alloy  in  a  larg:e  crucible,  adding- 
small  quantities  of  native  antimony  sulphide, 
until  three  or  four  times  the  weight  of  the  alloy 
has  been  reached. 

2.  A  lead-colored  alloy  of  gold  and  anti- 
mony is  formed;  place  it  in  a  clean  crucible, 
melt,  and  blow  a  current  of  air,  by  means  of  a 
bellows,  o\'er  its  surface. 

3.  Blow  g-ently  at  first;  a  current  strong- 
enoug-h  to  produce  visible  fumes  is  all  that  is 
necessary.     When  the  fumes  cease,   increase 


CHEMICAL    WORK    IN    DENTAL    LABORATORY.  505 

the  heat,  and  before  pouring;  out  the  gold 
throw  a  forcible  current  of  air  on  the  surface. 
In  case  the  alloy  be  found  now  malleable, 
but  stiff  or  elastic  and  of  dull  color,  platmuin 
is  probably  present  and  must  be  removed  by 
the  "wet  method,"  which,  in  general,  must  be 
used  when  it  is  desired  to  reduce  the  alloy  to 
pure  gold,  as  is  the  case  when  the  gold  to  be 
refined  consists  of  very  coarse  filings,  frag- 
ments of  plates  containing  large  quantities  of 
solder,  linings  with  platinum  pins  attached, 
particles  of  base  metals,  etc.,  etc.  Proceed  as 
follows  by  the  method  of  Watt:* 

1.  Dissolve  the  alloy  in  aqua  regia,  using 
four  parts  of  hydrochloric  to  one  of  nitric,  C.  P. 
acids  being  used.  The  chloride  of  silver  is 
found  as  a  grayish-white  powder  at  the  bottom 
of  the  vessel.  Let  settle,  and  pour  off  super- 
natant liquid. 

2.  Add  gradually  to  the  liquid  poured  off  a 
clear,  filtered  solution  of  ferrous  sulphate  in 
distilled  water.  Gold  is  precipitated  as  a 
brown  powder. 

3.  Let  settle,  filter,  wash  off  from  the  filter 
paper,  digest  in  dilute  sulphuric  acid,  filter 
again,  wash  well,  and  the  result  is  pure  gold. 

552.    To  determine  the  carat  of  an  alloy. — 

Multiply  24  by  the  weight  of  gold  in  the  alloyed  mass, 
and  divide  product  by  weight  of  the  mass.     Take,  for  ex- 

*  Quoted  by  Richardson. 


506  DENTAL    CHEMISTRY. 

ample,  a  solder  composed  of  6  parts  gold,  and  3  of  other 
ingredients:  the  weight  of  the  gold  is  represented  by  6, 
the  total  weight  g  /.  24  X  6  ^  9  =  16.  The  alloy  is,  then, 
16  carats  fine.  When  now  the  gold  is  not  pure,  attention 
should  be  paid  to  the  number  of  carats,  and  deduction 
made  accordingly.  Suppose  a  solder  contain  48  parts 
of  22  carat  gold,  and  28  parts  of  other  constituents;  here 
the  true  weight  of  the  gold  is  not  48,  but  44.  (22  carat 
gold  is  one-twelfth  alloy;  one-twelfth  of  48  is  4  and  48 — 

4  =  44)- 

553.  To  reduce  gold  to  a  required  carat:  multiply 
24  by  the  weight  of  pure  gold  used,  and  divide  the  product 
by  the  required  carat.  The  quotient  is  the  weight  of  the 
mass  when  reduced,  from  which  subtract  the  weight  of  the 
gold  used,  and  the  remainder  is  the  weight  of  the  alloy  to 
be  added.  For  example,  reduce  10  ounces  of  pure  gold  to 
18  carats:  24  X  10  -^  18  —  10  =  3.3  +  ounces  of  alloy  to 
be  added.  If  the  gold  is  not  pure,  allowance  must,  of 
course,  be  made  by  subtracting  as  in  the  previous  rule. 

554.  To  raise  gold  from  lower  to  higher  carat: 
Multiply  the  weight  of  the  alloyed  gold  used,  by  the  num- 
ber representing  the  proportion  of  alloy  in  the  given 
carat,  and  divide  the  product  by  that  number  representing 
the  proportion  of  alloy  in  the  required  carat;  the  quotient 
is  the  weight  of  the  mass,  when  reduced  to  the  required 
carat  by  adding  fine  gold. 

For  example,  suppose  it  is  required  to  raise  16  carat 
gold  to  18  carats:  in  16  carat  gold  there  is  24  —  16,  or  8, 
alloy;  in  18  carat  gold  there  is  24  —  18,  or  6,  alloy.  The 
example,  therefore,  becomes  i  X  8-^6=  l^;  that  is, 
add  ^  of  a  pennyweight  of  pure  gold  to  the  I  penny- 
weight of  16  carat  gold,  in  order  to  obtain  18  carat  gold. 

If,  now,  instead  of  adding  pure  gold  it  be  desired  to  add 
gold  of  some  particular  carat,  it  is  merely  necessary  to 
subtract  the  numbers,  as  16  and  18  above,  from  the  carat 
instead   of   from    24.     The    example    above    would    then 


CHEMICAL  WORK  IN  DENTAL  LABORATORY.     507 

become,  if  22  carat  gold  were  to  be  added,  i  X  6  -^  4  — 
i^,  that  is  to  each  pennyweight  of  16  carat  gold,  add  Y^ 
pennyweight  of  22  carat  gold. 

555.  Methods  of  preparing  dental  amalgam  alloys. — 

Take  a  Hessian  or  sand  crucible,  fuse  in  it  enough 
borax  to  fill  the  crucible  at  least  one-third  full,  melt  the 
tin  in  it  over  the  usual  dental  or  smelting  forge-fire  and, 
after  it  is  melted,  add  the  granulated  silver,  which,  pre- 
ferably, should  have  been  heated  to  a  low  redness.  The 
silver  soon  fuses  in  the  molten  tin  and  after  thoroughly 
stirring  with  an  iron  rod  or  clay  pipe-stem  of  small  size, 
the  copper,  in  form  of  small  pieces  of  wire,  should  be 
added.  After  it  has  melted,  and  the  mixture  has  been 
stirred,  the  gold  is  added,  melted,  and  all  is  thoroughly 
stirred.  After  fusion  and  mixing  is  complete,  quickly 
pour  the  fused  mass  into  a  broad,  open,  flat,  shallow 
receptacle  of  iron  or  soap  stone,  and  let  cool.    (Flagg). 

According  to  Flagg,  very  slozv  cooling  is  to  be  avoided, 
as  it  gives  rise  to  almost  complete  separation  of  the  silver 
from  the  tin,  or  in  other  words,  the  cohesion  of  like  mole- 
cules overcomes  the  adhesion  of  unlike  ones.  The  end 
sought  £or  is  to  fix  the  molecules,  as  much  as  possible,  in 
the  position  into  which  they  are  driven  by  the  heat. 
Prompt  cooling  secures  the  greatest  uniformity  of  distri- 
bution to  components.     (Flagg). 

Eflsig  prefers  to  melt  the  platinum  and  silver  together 
first,  in  case  platinum  is  used,  so  that  oxidation  of  the  tin 
may  not  take  place  at  the  instant  of  union  with  the  plati- 
num. After  the  platinum  and  silver  have  been  melted, 
the  tin  and  gold  are  to  be  added.  Borax  is  to  be  fused  in 
the  crucible  first  and,  lastly,  a  layer  of  broken  charcoal 
should  be  placed  over  the  mass  before  the  heating. 

556.  Alloys  and  amalgams :  tests:  the  tests  by  which 
good  amalgam  alloys  are  recognized  are  partly  chemical, 
partly  mechanical.  The  latter  will  not  be  considered  in 
this  work.     The  chemical  tests  include  the  quality  of  the 


508  DENTAL    CHEMISTRY. 

mercury.     Pure  mercury,   practically  free    from   metallic 
admixtures,  should  be  used. 

557.  Mercury  may  be  freed  from  mechanical  impuri- 
ties by  filtering  it  through  a  cone  of  paper,  round  the 
apex  of  which  a  few  pinholes  have  been  made.  Lead  may 
be  removed  from  it  by  exposing  the  mercury  in  a  thin 
layer  to  the  action  of  nitric  acid,  diluted  with  two  meas- 
ures of  water,  which  should  cover  its  surface  and  be 
allowed  to  remain  in  contact  with  it  for  a  day  or  two,  with 
occasional  stirring.  Wash  well  with  water,  dry  first  with 
blotting  paper,  then  by  gently  heating. 

For  effect  of  sulphuretted  hydrogen  on  alloys,  see  Sec- 
tion 530,  31.  Use  a  weak  solution  to  note  gradual  discol- 
oration. 

558.  In  testing  an  alloy  for  constituent 
metals,  first  make  a  preliminary  examination 
as  follows:  into  a  test  tube  drop  some  of  the 
metal  or  alloy  in  form  of  clippings,  or  coarse 
powder,  then  pour  m  some  C.  P.  nitric  acid; 
convenient  proportions  are  a  few  grains  of  the 
metal  to  a  drachm  or  two  of  the  acid;  warm 
over  an  alcohol  flame,  being  careful  not  to  let 
the  acid  boil  over  out  of  the  test-tube,  as  it  is 
very  corrosive  and  will  burn  hands,  clothing, 
etc.  Of  the  commoner  metals,  copper,  silver, 
and  zinc  will  be  dissolved.  If  the  copper  is  in 
any  noticeable  quantity,  the  solution  may  ac- 
quire a  green  or  blue  color.  Tin,  gold,  anti- 
mony, and  platinum  are  not  dissolved,  though 
traces  of  the  last  two  may  go  into  solution. 

559.  Short  method  of  qualitative  analysis  of  amal- 
gam alloys:  according  to  Eckfeldt  and  Dubois,*  an  idea 

*  Quoted  by  Flagg. 


CHEMICAL   WORK    IN    DENTAL    LABORATORY,  o09 

may  be  had  of  the  presence  of  gold  and  platinum  from 
the  action  of  the  tin,  which  is  not  dissolved;  but,  after  the 
action  of  the  acid  is  over,  shows  itself  as  a  whitish  pre- 
cipitate, colored  from  light  to  deep  purple,  if  gold  be 
present,  or  dirty-blackish  color,  \i  platinum  be  present  with 
or  without  gold.  After  some  idea  is  thus  gained,  take 
more  of  the  metal  or  alloy,  say  20  grains,  and  dissolve  in 
half  an  ounce  of  acid,  using  a  beaker.  It  is  advisable  to 
use  what  is  sold  as  C.  P.  nitric  acid,  strong.  The  beaker 
should  not  be  brought  into  contact  with  the  naked  flame 
in  warming;  it  may  be  passed  to  and  fro  through  the 
flame,  or  warmed  by  dipping  into  boiling  water.  After  the 
action  is  over,  evaporate  to  dryness  in  a  porcelain  dish 
over  the  water  bath,  a  copper  vessel  filled  with  water  under 
which  is  the  alcohol  flame.  The  whole  should  be  under 
a  "hood"  for  carrying  off  the  vapors,  or  in  a  well-vent- 
ilated room.  The  fumes  of  the  nitric  acid  are  very  irri- 
tating, and  should  not  be  breathed,  (i.)  After  the  nitric 
acid  mixture  has  well  evaporated,  which  will  take  some 
little  time  over  the  water-bath,  add  distilled  water,  stir 
well,  and  filter.  [Previous  work  has  revealed  the  presence 
or  absence  of  gold,  platinum,  and  tin;  there  remain  silver^ 
copper,  cadmium,  and  zinc  to  be  looked  for]. 

(n.)  After  filtering,  add  some  dilute  hydrochloric 
acid — a  few  drops  of  acid  in  a  test-tube  half  full  of  water 
will  be  enough — and,  '\isilvcr\s  plenty,  a  white,  curdy  pre- 
cipitate will  be  formed. 

(hi.)  Filter  again,  and  to  a  little  of  the  filtrate  (liquid 
which  goes  through  the  paper)  apart  from  the  rest,  add  a 
few  drops  of  ammonia  water  (made  by  mixing  one  vol- 
ume of  stronger  ■SLVCwaonvA.  water  with  three  volumes  of  dis- 
tilled water);  a  blue  color  indicates  copper. 

(iv.)  To  the  rest  of  the  filtrate  add  sulphuretted 
hydrogen.  After  the  sulphuretted  hydrogen  water  has 
been    added,  a   black  precipitate    of  copper  sidpJiide  will 


510  DENTAL   CHEMISTRY. 

result,  unless  modified  in  color  by  a  large  percentage  of 
cadmium. 

(v.)  Filter,  saving  the  filtrate,  wash  the  precipitate  off 
the  filter  paper  into  a  porcelain  dish,  using  the  wash  bottle 
(a  flask  with  a  perforated  cork  having  two  bent  glass 
tubes  passing  down  into  the  flask;  blowing  into  one  tube 
will  force  water  out  through  the  other  in  a  fine  stream). 
Boil  the  precipitate  in  the  porcelain  dish  with  sulphuric 
acid  diluted  with  water  ( one  part  of  acid,  added  very  slowly 
and  with  constant  stirring,  to  four  parts  of  water,  well 
jnixed,  allowed  to  stand  24  hours,  and  decanted). 

(vi.)  Filter,  and  add  sulphuretted  hydrogen  water  to 
the  filtrate,  and  thea  a  few  drops  of  ammonia;  a  bright 
yellow  precipitate  will  indicate  cadviiiwi.  Suppose  now 
that  when  testing  for  copper  as  above  (m.).  no  blue  color 
appeared  with  ammonia,  then  test  directly  for  cadmium, 
as  in  (iv),  which,  if  present,  will  appear  as  a  yellowish 
precipitate,  on  addition  of  the  sulphuretted  hydrogen; 
{browjtish-yelloiv  indicates  that  silver  has  not  been  com- 
pletely removed  by  precipitation  with  HCl). 

(vii.)  Go  back  now  to  the  filtrate  saved  in  (v)  and 
boil  it  down  until  nearly  dry  to  expel  sulphuretted  hydro- 
gen, then  add  a  little  pure  water,  and  solution  of  sodium 
carbonate  until  neutral  (shown  by  dipping  a  piece  of  red 
and  a  piece  of  blue  litmus  paper  into  the  mixture  which, 
when  neutral,  will  not  change  the  color  of  either  paper). 
A  white  precipitate  indicates  presence  of  zinc. 

The  above  described  process  will  enable  the  beginner 
to  test  the  various  dental  amalgam  alloys  for  the  presence 
of  those  metals  usually  found  in  them.  The  detection  of 
gold,  platimmi,  copper,  cadmium,  and  zinc  is  of  importance, 
for  all  the  alloys  contain  silver  and  tin.  It  is  desirable  to 
procure  a  sulphuretted  hydrogen  apparatus,  such  as  a  Kip 
generator,  and  some  Woulfe  bottles;  pass  the  gas  gene- 
rated through  a  Woulfe  bottle,  containing  a  little  water, 


CHEMICAL  WORK  IN  DENTAL  LABORATORY.     511 

SO  as  to    zvash  it,  then  directly  into  the  solution  to   be 
tested.* 

560.  Short  method  of  quantitative  analysis  of 
the  more  common  amalgam  alloys. 

1.  Estimate  the  mercury — of  an  old  amalgam,  for  ex- 
ample— by  weighing,  heating  to  redness,  weighing  again. 
The  loss  in  weight  indicates  the  weight  of  mercury  which 
was  present. 

2.  Estimate  the  tin  by  weighing,  heating  to  briglit  red- 
ness with  borax,  adding  potassium  nitrate  in  small  quan- 
tity, cooling,  collecting  button  and  globules,  weighing 
again.     The  loss  in  weight  indicates  the  weight  of  the  tin. 

3.  Estimate  the  silver  by  rolling  out  the  button  (ob- 
tained by  procedure  as  in  2)  into  a  thin  ribbon,  boil  in  a 
platinum  or  glass  vessel  with  at  least  two  or  three  times 
its  weight  of  concentrated  sulphuric  acid.  Continue  boil- 
ing until  the  acid  no  longer  attacks  the  metal,  let  settle, 
pour  off  supernatant  liLjuid,  save  the  residue.  Precipi- 
tate silver  from  the  poured-off  liquid,  by  dipping  plates 
of  copper  into  it.  Collect  the  silver,  wash  well,  heat, 
weigh. 

4.  Go  back  to  residue  obtained  in  3,  wash  well,  dis- 
solve in  aqua  regia,  drive  off  acid  by  evaporation,  dissolve 
in  a  large  quantity  of  distilled  water,  add  oxalic  acid,  the 
gold  is  thrown  down,  let  settle,  pour  off  supernatant  liquid 
and  save  it.  Collect  gold,  wash,  dry,  heat  to  redness, 
weigh. 

5.  To  the  supernatant  liquid  obtained  in  4,  add  ammo- 
nium chloride  as  long  as  there  is  any  precipitate.      Let 

*To  detect  mercury  in  form  of  vapor  given  off  from  amalgam 
alloys,  Haines  and  Talbot  have  used  ammonio-silver  nitrate,  a  drop 
or  two  of  which,  on  chemically  Pure  filter-paper^  they  find  will  detect, 
by  discoloration,  exceedingly  small  quantities  of  mercury.  Whether 
fillings  which  respond  to  this  test  are  hurtful  to  the  patient  or  not, 
must  be  decided  by  clinical  experience. 


512  DENTAL   CHEMISTRY. 

precipitate  settle,  filter,  wash,  dry,  and  weigh  the  precipi- 
tate. Every  lOO  parts  contains  44.28  of  platinum.  (Essig). 

6.  Estimate  the  percentage  of  each  metal  present  by 
dividing  the  weight  of  the  metal  found  by  the  weight  of 
the  amalgam  in  the  beginning,  before  anything  was  done 
to  it. 

561.  Tests  for  cements:  tests  should  be  made  both  of 
the  liquid  and  of  the  powder.  The  oxypJiospJiate  cements 
consist  usually  of  glacial  phosphoric  acid  and  oxide  of 
zinc.  Take  the  reaction  of  the  liquid  with  blue  litmus  to 
show  that  it  is  acid.  Pour  a  little  of  the  liquid  into  a 
test  tube,  and  holding  the  latter  inclined,  let  an  aqueous 
solution  of  a  little  egg-albumin  gradually  trickle  down  the 
side  of  the  tube  into  the  acid.  If  a  zone  of  whitish  turbid- 
ity is  noticed  at  the  juncture  of  the  two  liquids,  it  is 
glacial  phosphoric  acid,  rather  than  the  common  acid. 
To  prove  that  it  is  phosphoric  acid  rather  than  any  other, 
as  for  example,  lactic  or  hydrochloric,  add  to  a  little  of  it, 
solution  of  silver  nitrate,  and  a  white  precipitate  is  pro- 
duced; this  does  not  tell  it  from  hydrochloric,  but  further 
add  barium  chloride  solution,  and  if  glacial  phosphoric 
acid  is  the  one,  a  white  precipitate  will  be  produced. 
The  tests,  then,  for  glacial  phosphoric  acid  are  as  follows: 

1.  Coagulation  of  albumin. 

2.  White  precipitate  with  silver  nitrate. 

3.  White  precipitate  with  barium  chloride. 

[^// these  tests  should  be  successful;  hydrochloric  acid 
gives  two  of  them,  ( i  and  2)  but  not  three  if  pure.  Sulphuric 
acid  is  distinguished  by  the  heat  evolved  on  mixing  it 
with  water.  Nitric  acid  coagulates  albumin,  but  does  not 
answer  to  tests  2  and  3.  Common  phosphoric  acid,  "when 
pure,  does  not  answer  to  test  i,  nor  when  diluted  to  test  3, 
but  if  it  contains  sulphates  as  an  impurity,  will  answer  to 
test  3,  and  it  may,  if  not  pure,  answer  also  to  test  2.  The 
"vegetable"  acids  like  acetic,  lactic,  etc.,  etc.,  do  not  res- 


CHEMICAL    WORK    IN    DENTAL    LABORATORY.  513 

pond  to  test  l].  If  the  phosphoric  acid  is  in  form  of 
crystals,  dissolve  in  as  little  water  as  possible,  or  melt  by 
gentle  heat,  and  then  apply  the  test  as  above.  If  the  crys- 
tals are  dry,  drop  one  of  them  into  a  solution  of  ^^^  albu- 
min, and  if  a  cloudiness  or  turbidity  surrounds  the  crystal  as 
it  dissolves,  test  No.  i  is  successful.  At  red  heat  the 
crystals  should  volatilize.  As  to  \.\\&  purity  of  the  glacial 
acid:  r^;«;«^m«/ glacial  acid  is  a  hard,  glassy  mass,  but 
the  pure  is  softer  and  wax-like. 

The  acid  is  deliquescent,  and  dissolves  readily  in  water, 
and  in  alcohol. 

To  test  the  liquid  of  the  oxychloride  of  zinc  cements,  it  is 
necessary  to  show  that  it  contains  zinc  and  is  a  chloride. 
Take  the  reaction  of  the  liquid,  which  should  be  acid.  Pour 
a  little  of  the  liquid  into  a  test  tube,  and  didd  hydrochloric 
acid;  no  precipitate  should  be  noticed.  Next  add  sidpliur- 
ctted  hydrogen,  either  in  gaseous  form  or  in  solution,  and  no 
precipitate  should  be  noticed.  Take  a  fresh  amount,  to 
which  nothing  thus  far  has  been  added,  and  add  anwioniiim 
hydrate  (Aqua  Ammoniae*will  do),  ammonium  chloride,  and 
ammonium  sidp J iide\  a  a'/«V^  precipitate  should  be  noticed. 
N.  B.  The  precipitate  may  be  greenish  white,  if  there  is 
iron  present  as  an  impurity.  Now  take  still  another  sam- 
ple of  the  liquid,  and  cautiously  add  ammonium  hydrate, 
letting  it  trickle  down  the  side  of  the  tube,  and  a  delicate 
white  zone  of  turbidity  will  be  noticed.  Shake  it  or  add 
plenty  of  ammonia,  and  it  will  disappear.  All  these  tests, 
if  successfully  obtained,  show  presence  of  zinc;  confirm 
with  blow-pipe.  Next,  to  prove  that  it  is  a  chloride  of  zinc. 
Take  a  fresh  amount  of  the  liquid,  and  add  silver  nitrate 
to  it;  a  curdy,  white  precipitate  becoming  violet  on  ex- 
posure to  light,  and  soluble  in  (plenty  of)  ammonium 
hydrate,  shows  the  presence  of  a  chloride. 

In  testing  the  powder  used  in  both  oxyphosphate  and 
oxychloride  cements,  attention  should  be  paid  both  to  its 
ingredients   and    quality;    first,    prove    that    it    contains 


514  DENTAL    CHEMISTRY. 

zinc  by  dissolving  in  nitric  acid,  as  dilute  as  possible,  and 
testing  as  for  zinc  in  the  liquid,  or  by  means  of  the  blow- 
pipe. 

Next  as  to  quality:  its  specific  gravity  should  be  5.6,  *it 
should  turn  yellow  when  heated  in  a  test-tube,  and  be- 
come white  again  on  cooling.  Try  to  dissolve  a  little  in 
water,  and  notice  that  it  is  insoluble;  add  to  a  mixture  of 
it  with  water,  a  little  nitric  acid,  and  notice  that  it  is  dis- 
solved completely.  To  the  solution  thus  obtained  in  nitric 
acid,  {\)  2t.dd  silver  nitrate :  no  precipitate  .should  appear; 
to  a  fresh  amount  of  the  nitric  acid  solution,  (2)  add 
barium  chloride:  no  precipitate  should  appear.  Now  take 
a  fresh  amount  of  the  powder,  add  water  to  it,  and  a 
few  drops  of  hydrochloric  acid:  then  add  (3)  sidphuretted 
hydrogen:  there  should  be  no  discoloration;  to  a  fresh 
amount  of  hydrochloric  acid  solution,  add  (4)  potassium 
ferrocyanide.  A  precipitate  appearing  should  not  be  col- 
ored green  or  blue.  Test  (i)  is  for  chlorides,  (2)  for 
sulphates,  (3)  for  lead,  (4)  for  iron. 

562.  Manipulation  of  vulcanite,  etc.:  much  in  re- 
gard to  this  subject  belongs  properly  to  mechanical 
dentistry.  When  the  rubber  is  ready  for  hardening  or 
vulcanizing,  the  latter  may  be  accomplished  by  submit- 
ting it  for  a  time  to  the  action  of  hot  air,  steam,  or  hot 
water.  A  strong  boiler  called  a  Vulcanizer  is  usually 
used,  the  metal  of  which  should  preferably  be  wrought. 

563.  To  improve  the  color  of  rubber,  Wildman  advises 
exposing  to  action  of  alcohol  in  sunlight  from  six  to 
twelve  hours.  Bending  hard  rubber  may  be  accomplished 
after  heating  to  the  proper  temperature  as  240*^  to  280°  F. 
Small  pieces,  uniformly  thick,  may  be  softened  by  oiling 
and  holding  over  the  flame  of  a  spirit  lamp.  Large  pieces 
or  those  of  irregular  thickness  may  be  softened  by  im- 
mersing in  oil  in  a  vessel  and  raising  to  the  required 
temperature. 

♦Determine  the  specific  gravity  according  to  Chapter  I. 


CHEMICAL   \VORK    IN    DENTAL    LABORATORY.  515 

564.  Parting  the  plaster:  an  ounce  of  castile  soap 
(cut  into  thin  shavings)  dissolved  in  a  pint  of  water,  by 
boiling,  is  used  for  parting  the  plaster. 

565.  Coloring  plaster:  to  color  plaster  add  a  little 
vermilion  or  burnt  umber  to  the  dry  plaster. 

566.  Hardening  the  plaster:  the  operation  may  be 
hastened  by  mixing  thick,  adding  common  salt,*  or  using 
hot  water,  or  by  combining  the  three  methods. 

567.  Compounding  rubber:  caoutchouc  may  be  mixed 
with  sulphur  and  the  coloring  matter,  either  by  passing 
repeatedly  between  steam-heated  rollers  or  by  reducing 
the  caoutchouc  in  the  first  place  to  a  pulpy  or  gelatinous 
state  (by  the  action  of  some  such  substance  as  carbon  di- 
sulphide)  and  then  mixing  the  sulphur  and  coloring  mat- 
ter with  it.  [VVildman  prefers  to  soften  caoutchouc  in  oil 
of  turpentine  or  in  equal  parts  of  coal  naphtha,  or  benzine, 
and  oil  of  turpentine].  From  5  to  50  per  cent,  of  alcohol 
should  be  added  to  the  solvent,  in  order  that  the  latter 
may  be  at  least  partially  recovered  after  the  caoutchouc 
has  softened.  Wildman  levigates  the  coloring  matter  and 
sulphur  in  spirits  of  turpentine,  first  grinding  the  coloring 
matter  to  a  fine  powder,  then  adding  the  sulphur  and 
grinding  thoroughly.  He  next  adds  a  little  of  the  pulpy 
caoutchouc,  mixes  thoroughly,  and  so  on. 

568.  Substances  used  to  color  rubbers:  the  natural 
color  of  hard  rubber,  composed  of  caoutchouc  and  sulphur 
only,  is  a  dark  brown.  Red  oxide  of  iron  and  also  vermil- 
ion are  used  to  make  red  rubbers;  cadmium  sulphide  to 
make  a  yellow,  and  with  oxide  of  zinc  to  make  a  lighter 
yellow.  Ivory  black  is  used  to  produce  a  black  rubber. 
Various  modifications  of  the  different  colors  may  be  made 
by  combining  the  coloring  materials  in  different  pro- 
portions. 

569.  Testing  rubbers  chemically :  to  ascertain  whether 
♦Addition  of  salt  is  said  to  weaken  the  plaster. 


516  APPLICATION   OF   CHEMISTRY   TO   DENTISTRY. 

metallic  mercury  is  set  free  in  the  body  of  the  rubber  by 
the  decomposition  of  the  sulphide  (vermilion)  during 
vulcanization,  a  simple  method  is  to  digest  the  rubber  in 
nitric  acid,  then  test  the  solution  for  mercury  in  the  usual 
way*  Sulphuretted  hydrogen  may  be  proved  to  be 
given  off  during  vulcanization  by  heating  a  sample  of  the 
rubber  to  320°F.,  for  one  hour  and  a  quarter  in  a  suitable 
receptacle,  and  collecting  the  gas  in  a  solution  of  a  lead 
salt.  A  black  precipitate  indicates  formation  of  sulphur- 
etted hydrogen. 

■ 1 

*Prof.  Salisbury  says  that  some  of  his  students  have  used  the  cop- 
per test  for  mercury  in  rubbers:  no  response  to  the  test  has  been  ob- 
tained before  vulcanizing,  but  after  vulcanization  evidence  of  abund- 
ance of  mercury  has  been  obtained,  showing  a  change  to  have  taken 
place  to  a  more  soluble  compound  or  to  metallic  mercury. 


PHYSIOLOGICAL   CHEMISTRY.  517 


CHAPTER  XIV. 
Laboratory  Work  in  Physiological  Chemistry. 

This  chapter  will  deal  with  carbohydrates,  fats 
and  oils,  fatty  acids,  proteids,  digestion  of  pro- 
teids,  examination  of  the  gastric  juice,  and  the 
blood. 

carbohydrates. 

Read  paragraphs  387  to  391  inclusive. 
Exercise  1.  Starch:— 

A.  Show  that  wheat  flour  contains  starch  by 
kneading  flour  in  a  thin  calico  bag  under  water. 
The  starch  passes  out  with  the  water,  forming 
a  milky  liquid  from  which  it  deposits  on 
standing. 

(There  remains  in  the  bag  a  sticky,  gray,  tenacious 
mass  composed  of  what  is  called  gluten,  a  nitrogenous 
substance  which  soon  decomposes,  and  smells  badly. 
See  Proteids). 

B.  Let  the  starch  obtained  in  A  settle,  pour 
off  the  water,  and  let  dry.  Then  take  a  little  of 
it,  and  rub  it  up  in  a  mortar  with  a  little  water. 
It   first    becomes  sticky,  but,  if  more  water  be 


518  DENTAL    CHEMISTRY. 

added,  mixes  with  it.  Prove  that  it  is  a  mix- 
ture and  not  a  solution  by  letting  it  settle,  and 
noting  the  bulk  of  the  sediment.  Decant  off 
the  supernatant  liquid,  filter,  and  add  to  the 
filtrate  dilute  tincture  of  iodine.  No  blue  color 
appears,  hence  starch  is  absent  from  the  sol- 
ution. 

C.  Go  back  to  the  starch  mixture  made  in 
B,  and  boil  a  little  of  it,  so  as  to  make  a  thin 
paste.  Let  cool.  Add  a  few  drops  of  the  di- 
lute tincture  of  iodine,  or  of  an  aqueous  solu- 
tion of  iodine,  and  note  deep  blue  color.  Boil, 
and  the  color  disappears. 

These  experiments  show  that  starch  is  rec- 
ognized by  its  reaction  with  iodine,  and  that 
it  is  not  soluble  in  cold  water. 

D.  Prepare  starch  from  potatoes  as  follows:  grate  the 
potatoes  to  a  pulp  on  a  common  tin  grater,  steep  the 
pulp  in  water,  and  squeeze  through  coarse  unbleached 
muslin. 

Steep  several  times,  and  strain,  collecting  the  liquid 
strained  each  time  ;  or  rub  the  softened  pulp  in  a  sieve 
under  a  current  of  water,  which  washes  out  the  star  ch 
In  either  case  let  the  washings  settle  half  an  hour  or  so, 
and  the  starch  will  deposit  slowly  to  the  bottom  of  the 
glass.  Pour  off  the  supernatant  liquid,  add  fresh  wa- 
ter, stir  well,  and  let  settle  again.  This  may  be  done 
several  times,  until  the  starch  is  clean  and  white,  when  it 
may  be  dried  in  a  clean,  shallow  dish. 

E.  Examine  starch  from  different  pi  ts  under  the 
microscope,  using  ^-inch  objective,  and  notice  the  con- 
centric layers  of  the  granules,  and  the  differences  in  size^ 


PHYSIOLOGICAL   CHEMISTRY.  519 

shape,  general  appearance,  distinctness,  and  character  of 
the  rugae,  and  position  of  the  more  or  less  central  point 
called  the  hilum. 

Exercise  2.  Action  of  dilute  acids  on  starch. 

A.  Mix  a  grain  or  two  of  starch  with 
half  a  test-tube  full  of  cold  water.  Add  one 
drop  of  sulphuric  acid,  and  boil  about  five  min- 
utes. No  mucilage  is  formed.  Remove  some  of 
the  liquid,  let  cool,  aiid  test  with  the  iodine 
solution.  The  deep  blue  color  is  not  obtained, 
but,  instead,  a  bliie-violet.  Continue  the  boil- 
ing, and  notice  that  on  testing  the  cooled  liquid, 
from  time  to  time,  the  color  reaction  with  iodine 
grows  less  and  less  marked,  and  finally  disap- 
pears. 

Starch,  when  heated  with  dilute  acids,  is  converted  first 
into  dextritie,  and  finally  into  dextrose. 

Solutions  of  dextnV/^,  containing  unchanged  starch, 
give  a  vinous-purple  reaction  with  iodine,  but  solutions 
of  dtyiirose  give  no  reaction  at  all.  Dextn'w^  is  a  gum- 
like substance,  deyiirose  is  a  sugar. 

B.  Boil  for  an  hour  the  liquid  described  in 
A.  Neutralize  the  acid  by  adding  chalk  in  ex- 
cess, pouring  the  liquid  into  a  beaker,  and  warm- 
ing. Filter,  and  evaporate  filtrate  nearly  to  dry- 
ness on  water  bath.  Let  cool,  and  notice 
sweet  taste,  (dextrose). 

C.  To  one  fluidrachm  of  Haines's  solution 
(Ex.  8)  add  one  or  two  drops  of  the  sweet-tast- 
ing residue,  and  boil.  A  bright  yellow  color  in- 
dicates presence  of  dextrose. 


520  DENTAL    CHEMISTRY. 

Exercise  3.  Action  of  Strong  Acids  on  Starch. 

A.  Add  excess  of  strong  sulphuric  acid  to  starch,  say 
5  cc.  of  acid  to  i  gramme  of  starch,  and  heat  to  boiling  in 
a  large  flask.  Note  that  the  experiment  resembles  a  pre- 
vious one,  Chapter  VII.  A  black  mass  is  soon  produced. 
Heat  still  further,  and  note  fumes  of  sulphurous  oxide, 
and  that  finally  a  colorless  liquid  results. 

B.  Pour  a  mixture  of  15  c.c.  strong  nitric  acid  and  35 
cc.  of  water  on  10  grammes  of  sugar  in  a  200  c.c.  flask. 
Heat  gently  until  the  reaction  begins  (copious  red 
fumes),    Then  withdraw  heat. 

When  the  red  fumes  no  longer  escape,  transfer  the 
liquid  to  an  evaporating  dish,  and  evaporate  to  one-half 
its  volume.  Let  cool.  Crystals  separate  on  cooling, 
which,  when  tested,  will  be  found  to  be  oxalic  acid. 

Exercise  4.  Action  oflieat  on  starcli. 

Heat  5  to  10  grammes  of  starch  in  a  porcelain 
dish  on  a  sand-bath,  with  constant  stirring,  not  al- 
lowing it  to  burn.  The  starch  turns  yellowish-' 
brown.  Heat  for  ten  minutes  after  the  starch  is 
uniformly  yellowish  brown,  allow  to  cool,  add 
water,  and  boil.  Dilute  and  filter.  Note  that  the 
filtrate  is  precipitated  by  alcohol. 

The  starch  in  this  experiment  is  converted  into  dex- 
trine or  "British  gum,"  the  ingredient  of  mucilage  of 
commerce.  Farinaceous  foods  for  infants  are  made  by 
baking  flour,  in  order  to  convert  the  starch  into  dextrine. 

Exercise  5.  Action  of  ferments  on  starch. 

A.  Note  the  action  of  malt  on  starch  as  follows: 
treat  50  grammes  of  pale,  ground  malt  with  500 
c.c.  of  cold  water  for  an  hour,  with  occasional 
stirring.  Then  heat  the  solution  to  60°,  C.  keeping 


PHYSIOLOGICAL    CHEMISTRY  521 

at  that  temperature  for  half  an  hour.  Filter 
through  a  dry  filter.  Now  make  a  thin  starch 
paste,  by  boiling  in  each  of  three  flasks  0.1 
gramme  of  starch  in  100  c.c.  of  water.  When 
the  starch  is  thoroughly  gelatinised  in  each  flask, 
add  10  c.c.  of  the  malt  infusion  to  one,  15  c.c.  to 
another,  and  20  c.c.  to  the  third.  Maintain  the 
flasks  at  a  temperature  of  50°  C  for  three  hours. 
Then,  on  a  porcelain  plate,  test  a  drop  or  two 
from  each  with  solution  of  iodine.  If  no  blue  or 
brown  coloration  is  obtained  from  any  one  of  the 
flasks,  it  is  plain  that  the  starch  has  been  convert- 
ed. If  a  color  is  obtained  from  any  one,  it  shows 
that  the  conversion  is  incomplete,  more  malt  sol- 
ution is  to  be  added,  and  the  heating  repeated 
for  three  hours  longer.  Finally  evaporate  the 
solution  to  very  small  volume  and  note  sweetish 
taste.    Test  it  with  Haines's  solution  as  before. 

B.  Repeat  experiment  A  heating  the  malt  to  boiling 
beforehand.     No  change  to  sugar  takes  place. 

C.  Repeat  experiment  A  previously  adding  a  little 
strong  sulphuric  acid  to  the  malt.  No  change  to  sugar 
takes  place. 

D.  Repeat  experiment  A  previously  adding  a  little 
strong  potassium  hydroxide  solution  to  the  malt,  until 
the  reaction  is  strongly  alkaline.  No  change  to  sugar 
takes  place. 

These  experiments  show  that  malt  contains  a  princi- 
ple which  has  the  property  of  converting  starch  into 
sugar,  and  that  this  property  is  destroyed  by  high  heat, 
strong  acids,  and  strong  alkalies. 


522  DENTAL    CHEMISTRY. 

Exercise  6.  Action  of  the  saliva  on  starch^ 

A.  Perform  the  test  outlined  in  paragraph  571, 
A,  1  to  3. 

B.  Boil  the  saliva  first,  then  add  starch,  and 
lay  aside  as  in  A,  subsequently  testing  for  sugar. 
No  reaction  is  obtained,  owing  to  the  action  of 
heat  on  the  salivary  ferment. 

C.  Add  a  little  strong  sulphuric  acid  to  the 
saliva  first,  then  add  starch,  and  go  on  as  in  A. 
No  reaction  for  sugar  is  obtained. 

D.  Repeat  C,  substituting  concentrated  solu- 
tion of  potassium  hydroxide  for  the  acid.  No 
sugar  reaction  is  obtained. 

E.  Perform  experiment  A  with  raw  starch 
.instead  of  the  boiled  paste.  No  sugar  reaction 
is  obtained. 

These  experiments  show  that  the  saliva  contains  a 
principle  which  has  the  property  of  converting  starch 
into  sugar  ;  that  this  property  is  destroyed  by  heating 
above  35°to40°  (95°toi04°),  by  strong  acids,  and  by 
alkalies.  Moreover  the  ferment  is  without  action  on  raw 
starch. , 

Exercise  1.  Action  of  the  pancreatic  fluid 
on  starch. 

A.  Repeat  the  experiment  with  starch,  describ- 
ed in  paragraph  571,  A,  1  to  3,  using,  however, 
pancreatic  extract  instead  of  saliva. 

Good  Pancreatic  extract  for  this  purpose  can  be  made 
according  to  Long  by  cutting  a  hog's  pancreas  into 
small  pieces,  and  passing  these  through  a  small  sausage 
mill.    Take  about  lo  grammes  of  the  finely  divided   mat- 


-PHYSIOLOGICAL    CHEMISTRY.  523 

ter,  and  cover  with  50  c.c.  of  25  per  cent,  alcohol.  Let 
stand  a  week,  filter,  evaporate  alcohol  at  low  temperature, 
take  up  residue  with  50  c.c.  of  water,  and  use  this  solution 
for  the  experiment. 

B.  Repeat  the  experiment,  boiling  the  pan- 
creatic solution  first.  No  sugar  reaction  is  ob- 
tained. 

Exercise  8.  The  sugars  in  solution. 

A.  Make  up  solutions  for  testing  sugars  as  fol- 
lows : — 

1.  Haines's  solution  i^dissolve  30  grains  of 
pure  sulphate  of  copper  in  one  half  a  fluidounce 
of  pure  water;  make  a  perfect  solution,  and  add 
to  it  one  half  a  fluidounce  of  pure  glycerine,  mix 
thoroughly,  and  add  five  fluidounces  of  liquor 
potassse.  (See  paragraph  163).  This  solu- 
tion is  used  for  qualitative  work  and  is  permanent, 
after  being  decanted  from  reddish  precipitate 
which  takes  place  after  a  time. 

2.  Fehling's  solution: — dissolve  69.28  gram- 
mes of  pure  recrystallized*  cupric  sulphate  in 
distilled  water  sufficient  to  make  the  solution 
measure  just  one  liter.  Keep  in  a  well  stoppered 
flask  labelled  I.  Next  dissolve  100  grammes  of 
sodium  hydroxide,  precipitated  by  alcohol,  in 
500  c.c.  of  water,  heat  to  boiling,  and  add  grad- 
ually 350  grammes  of  pure  recrystallized  Rochelle 
salt.  (See  paragraph  445).  Stir  until  all  is  dis- 
solved.   Let  solution  stand  24  hours  in  a  covered 

♦Necessary  on  account   of   presence   of   ferrous   sulphate  in  most  commercial 
samples. 


524  DENTAL    CHEMISTRY. 

vessel,  filter  through  asbestos  into  a  liter  flask, 
and  add  pure  water,  enough  to  make  the  solution 
measure  just  one  liter,  keep  in  a  well-stoppered 
bottle  labelled  11. 

When  about  to  use  it,  mix  equal  parts  of  the 
two  solutions.  The  mixture  will  then  contain 
34.64  milligrammes  cupric  sulphate  in  each  cubic 
centimeter  of  liquid. 

This  mixed  solution  is  used  both  for  qualitative  and 
quantitative  work.     It  is  not  permanent. 

B.  Make  up  solutions  of  sugars  to  be  tested 
as  follows:  dissolve  one  gramme  each  of  grape- 
sugar  (dextrose),  cane-sugar  (saccharose),  and 
milk-sugar  (lactose)  in  lOOc.c.  of  distilled  water. 
Note  that  the  milk-sugar  is  dissolved  less  readily 
than  the  other  two.     Test  as  follows: — 

1.  Boil  one  fluidrachm  of  Haines's  solution 
which,  if  properly  made,  should  not  change 
when  boiled.  Add  to  the  boiling  solution,  drop 
by  drop,  8  to  10  drops  of  each  of  the  solu- 
tions of  sugar  above  described.  As  each  drop 
is  added  shake,  and  boil  a  few  seconds. 
Finally  when  the  whole  8  or  10  drops  have 
been  added,  boil  for  30  seconds. 

Compare  the  reactions  obtained  with  the 
different  sugars,  and  it  will  be  found  that  the 
grape-sugar  (dextrose)  makes  the  solution  tur- 
bid on  addition  of  the  second  drop,  and,  on 
adding  further  drops  and  boiling,  a  reddish  violet 
tint   appears;  finally  after  8  drops    have    been 


PHYSIOLOGICAL    CHEMISTRY.  525 

added,  and  the  solution  boiled  30  seconds,  a 
brick-red  precipitate  (cuprous  oxide^  appears, 
which  acquires  a  brighter  tint  as  the  tube  cools, 
and  soon  settles  to  the  bottom,  leaving  a  clear 
liquid  above.  The  grape-sugur  (dextrose,  glu- 
cose) is  said  to  reduce  the  alkaline  copper  solu- 
tion, cupr^//5  oxide,  CuO,  being  thrown  down. 
Milk-sugar  (solution  1  to  100)  acts  in  a  similar 
way  with  Haines's  solution  yet  if,  after  boiling, 
the  solution  beheld  up  to  reflected  light,  a  dis- 
tinctly bluish  tint  can  be  seen.  Milk-sitgar  re- 
duces the  copper  solution  more  slowly  than 
grape-sugar.  Cane-sugar  does  not  affect  the 
brilliant  blue  color  of  the  solution  at  all. 

2.  Test  the  same  three  solutions  with  Fehling's  solu- 
tion, as  follows: — Heat  lo  c.c.  of  the  solution  to  boiling, 
and  when  boiling,  add  i  cc.of  each  solution  of  sugar. 

The  principle  of  all  the  alkaline  copper  tests  is  the  same 
namely  the  reduction  of  the  cupric  sulphate  to  cuprous 
oxide. 

4.  Boil  a  little  of  the  solution  of  cane  sugar  with  a  few 
drops  of  hydrochloric  acid,  neutralize  with  sodium  car- 
bonate, and  then  apply  the  three  tests  as  above.  It  will  be 
found  that  the  cane  sugar  now  reduces  the  alkaline 
copper  liquids,  its  molecule  being  split  up  into  reducing 
sugars,  dextrose  and  levulose. 

3.  Subject  the  sugar  solutions  to  Trommer's  test  as 
follows:  — 

Add  to  4  cc.of  each  sugar  solution  enough  cupric  sul- 
phate solution  to  impart  to  it  a  very  faint  greenish-blue 
tint,  and  considerable  excess  of  strong  potassium  hydro- 
oxide  solution.  Warm  the  mixture,  and  continue  the 
heat  to  boiling. 


526  DENTAL    CHEMISTRY. 

Note  the  difference  in  action  of  the  different  sugar 
solutions,  dextrose  giving  a  yellowish  precipitate,  which 
grows  bright  red  on  boiling. 

Exercise  9.  Fermentation  of  sugars. 

A.  Measure  off  120  c.c,  each  of  solutions  of 
the  three  sugars,  in  strength  2  grammes  of  sugar 
to  500  c.c.  of  water.  Next  add  to  each  sugar 
solution,  a  two-cent  cake  of  compressed  yeast 
in  small  fragments;  shake  up  well,  and  take  the 
specific  gravity.  Set  aside  in  a  warm  place,  not 
cooler  than20°C  (68°F),  for  24  hours.  At  the 
end  of  that  time  note  that  in  the  bottle  contain- 
ing solution  of  grape-sugar,  there  is  escape  of 
gas  bubbles,  and,  if  the  flask  is  provided  with  a 
stopper  and  twice  bent  delivery  tube,  the  latter 
dipping  into  lime  Avater,  a  precipitate  of  calcium 
carbonate  will  be  formed.  The  molecule  of 
grape-sugar  is  split  up,  as  follows: — 

C6H,306=2C,H5HO+2CO, 
Note  the  alcoholic  odor  of  the  mixture. 

Take  the  specific  gravity,  and  it  will  be  found 
to  be  much  less  than  before  fermentation. 

On  the  other  hand  note  absence  of  any  fer- 
mentative change  in  the  bottles  containing  cane 
sugar,  and  milk  sugar. 

B.  Pour  some  of  the  mixture  of  grape-sugar  solution 
and  yeast,  before  fermentation,  into  a  flask,  and  heat  to 
boiling.  Let  stand  for  24  hours,  and  note  absence  of 
fermentative  change.  The  high  heat  has  destroyed  the 
activity  of  the  yeast  germ.  To  another  portion  of  the 
grape-sugar  solution  and  yeast,  before  fermentation,  add 


PHYSIOLOGICAL    CHEMISTRY.  527 

strong  alcohol,  and  note  absence  of  fermentative  change 
in  24  hours,  the  alcohol  destroying  the  activity  of  the 
yeast  cell.  This  explains  why  wines  containing  a  large 
percentage  of  alcohol  "  keep  "  well. 

C.  Let  the  fermented  solution  of  grape-sugar  stand 
three  or  four  days  more  in  a  warm  place,  and  note  disap- 
pearance of  alcoholic  odor,  and  the  presence  of  a  sour 
smell.  This  is  due  to  acetic  acid  ferme?itatio?i.  (See  para- 
graph 420). 

D.  Study  lactic  fermentation,  paragraphs  436,  and  438. 
Exercise  10.  Glycogen. 

A.  Glycogen  is  a  white,  tasteless,  inodorous,  and  am- 
orphous powder,  obtained  from  the  liver. 

B.  Test  the  solubility  of  glycogen  in  alcohol,  ether, 
cold  and  boiling  water. 

C.  To  a  solution  of  glycogen  in  water  add  a  little  io- 
dine solution,  and  note  the  red  color  produced.  Heat 
the  mixture,  and  the  color  disappears. 

D.  Boil  solution  of  glycogen  for  10  minutes  with  di- 
lute hydrochloric  acid;  nearly  neutralize  the  acid,  cool, 
and  test  with  iodine  solution.  No  color  appears,  the 
glycogen  having  been  converted  into  sugar. 

Exercise  11.  Fats  and  Oils:— 

A.  Knead  beef  or  mutton  suet  in  a  muslin  bag 
in  a  basin  of  hot  water;  the  fat  melts,  and  passes 
out,  leaving  the  membrane  or  tissue  in  the  bag. 
Let  the  melted  fat  cool,  when  it  will  solidify  and  is 
then  known  as  tallow.  Obtained  from  hogs  the 
fat  is  known  as  lard,  and  is  much  softer.  These 
fats  together  with  human  fat  are  mixtures  of 
palmifin  and  stearin,  together  with  olein, 
the  first  two  being  solids  but  olein  a  liquid  at 
ordinary  temperatures,  hence  the  solid  or  liquid 


528  DENTAL    CHEMISTRY. 

condition  of  a  fatty  substance  is  determined  by 
the  relative  quantity  of  the  three  fats  just 
mentioned  present  in  it.  Tallow  is  hard  be- 
cause it  contains  a  relatively  large  proportion 
of  stearin  and  palmitin. 

B.  Take  a  piece  of  tallow  or  lard,  and  note 
that  it  stains  paper  permanently. 

C.  Weigh  out  six  small  samples  of  tallow, 
all  of  the  same  weight,  place  in  six  test-tubes, 
and  pour  into  the  tubes  water,  alcohol,  hot 
alcohol,  ether,  carbon  disulphide,  and  benzene 
(paragraph  319)  respectively.  Notice  that  the 
fat  floats  on  water,  and  is  insoluble  in  it,  that 
it  is  less  soluble  in  alcohol  than  in  ether,  or  the 
remaining  solvents,  and  that  is  more  soluble 
in  hot  alcohol  than  in  cold. 

D.  Obtain  a  little  lanolin  (wool-fat),  and  mix  it  with 
twice  its  weight  of  water.  Notice  that,  unlike  other  fats, 
it  mixes  with  the  water. 

Lanolin  differs  from  other  fats  in  that  it  does  not  con- 
tain glycerin,  but  two  alcohols  of  the  same  formula 
(isomeric)  C26  H43  HO,  known  as  cholcsterin  and  iso-cholcst- 
erin. 

E.  Keep  samples  of  butter  and  of  lanolin  in  a  warm 
place  for  some  days.  Note  that  the  butter  becomes 
rancid,  undergoing  a  kind  of  fermentation,  resulting  in 
liberation  of  hutytic  acid.  The  lanolin  does  not  become 
rancid  so  readily. 

Exercise  12.  Saponiflcatioii. 

A.  Prepare  hard  soap  as  follows: — Weigh  out 
50  grammes  of  olive  oil,  mix  with  60  c.c.  of  a  1 5 


PHYSIOLOGICAL    CHEMISTRY.  529 

per  cent,  solution  of  sodium  hydroxide,  and  boil 
for  at  least  an  hour.  Then  add  solution  of  1 5 
grammes  sodium  chloride  in  40  c.c.  of  water, 
and  boil  again,  but  only  for  a  short  time.  The 
soap  formed  by  action  of  the  alkali  rises  to  the 
surface  of  the  saline  solution  in  which  it  is  in- 
soluble, and  solidifies  on  cooling. 

The  equation  is  as  follows: 
C3H5(C,sH330,)3+3NaHO=3NaC,8H330,+C3H5(HO)3 

olive  oil  hard  soap  glycerin 

Olive  oil  is  the  oleate  of  tritenyl  or  glyceryl  (paragraph 
369);  when  acted  on  by  sodium  hydroxide,  sodium  oleate 
(hard  soap)  and  glycerin  are  formed,  the  latter  being  a 
hydroxide  of  the  radical  glyceryl. 

B.  Soft  Soap.  Prepare  soft  soap  as  follows: — Boil  25 
grammes  of  tallow  with  a  solution  of  10  grammes  of 
potassium  hydroxide  in  25  c.  c  of  water. ,  Stir  until  no  more 
oil  globules  are  seen  floating  on  top  of  the  water,  and  add 
water  from  time  to  time  to  make  up  for  that  lost  by 
evaporation.  Soft  soap,  excess  of  alkali,  and  glycerol  are 
the  products. 

Exercise  13.  Glycerol  (Glycerin). 

A.  Prepare  glycerin  on  a  small  scale  by  mixing 
a  little  fat  with  fmely  powdered  litharge  and 
water  in  a  porcelain  dish.  Heat.  Lead  plaster 
is  formed,  and  glycerin  remains  in  solution  in  the 
water.  Filter.  Pass  a  current  of  sulphuretted 
hydrogen  through  the  filtrate,  evaporate  to  small 
bulk,  and  filter  again.  Note  the  sweetish  taste 
of  the  filtrate. 

In  the  above  experiment  it  is  convenient  to 


530  DENTAL    CHEMISTRY, 

take  50  c.c.  of  cottonseed  oil,  25  grammes  of 
litharge,  and  1 00  c.c.  of  water,  more  of  the  latter 
being  added  from  time  to  time  as  needed. 

Glycerin  of  commerce  is  not  made  in  this  way,  but  by 
passing  superheated  steam  into  melted  fats,  which  is  de- 
composed into  glycerin  and  fatty  acid. 

B.  Examine  the  solvent  power  of  glycerin  (paragraph 
369)  as  follows: — 

1.  Weigh  out  20  grammes  of  tannic  acid,  and  add  it  to 
100  c.  c.  of  glycerin. 

2.  Mix  20  c.  c.  of  liquefied  carbolic  acid  with  looc.  c.  of 
glycerin. 

3.  Mix  the  same  proportions  of  creasote  and  glycerin, 
and  note  that  the  creasote  does  not  dissolve  in  the  gly- 
cerin. 

4.  Mix  6  grammes  of  boracic  acid  with  9  grammes  of 
glycerin.  Heat  in  a  porcelain  dish  on  a  sand-bath  at 
150°  C.  (302°  F),  stirring  v.ell,  until  no  more  aqueous 
vapors  are  given  off.  A  homogeneous,  transparent  mass 
is  formed  which  is  boroglyceride ;  for  equation  and  uses 
see  paragraph  371. 

5.  Test  any  liquid  supposed  to  contain  glycerin  by 
mixing  with  zinc  carbonate,  and  drying  at  the  tempera- 
ture of  the  water  bath.  Extract  the  dried  mass  with  ab- 
solute alcohol,  evaporate,  and  obtain  a  sweetish  residue. 

Exercise  14.  The  Fatty  Acids. 

A.  Dilute  the  soft  soap  mixture  described  in  Exer- 
cise 12,  with  water,  and  to  about  25  c.c.  of  the  mixture  add 
10  c.c.  of  strong,  commercial  hydrochloric  acid,  and  warm 
on  the  water  bath.  Liberated  fatty  acids  collect  on  the 
surface.  If  more  water  now  be  added,  and  the  whole 
allowed  to  cool,  a  semi-solid  layer  of  fatty  acids  can  be 
lifted  from  the  surface  of  the  liquid. 

B.  Add  a  little  of  the  fatty  acids  obtained  above  to  a 


PHYSIOLOGICAL    CHEMISTRY.  531 

solution  of  rosanilin  hydrochloride,  and  warm: — note  the 
dark-red  or  reddish-black  color. 

C.  Make  a  saturated  solution  of  the  fatty  acids  (ob- 
tained in  A)  in  alcohol  by  warming.  Let  cool,  and  ob- 
tain crystalline  scales. 

Exercise  15.  Emulsions. 

A.  Shake  up  a  little  olive  oil  in  a  test-tube  with 
some  white  of  Qgg.  Note  that  the  liquids  mix, 
forming  a  white  mass  known  as  an  enmlsion. 

It  is  by  emulsification  in  the  small  intestines  that  fatty 
substances  are  brought  into  a  condition  in  which  they 
can  be  absorbed  by  the  lacteals.  The  process  is  brought 
about  by  the  pancreatic  juice  and  bile,  as  may  be  shown 
by  rubbing  up  oil  in  a  mortar  with  fresh,  finely  divided 
pancreas. 

B.  Examine  a  drop  of  the  emulsion,  obtained  in  A, 
under  the  microscope: — small  globules  are  seen,  varying 
in  size  and  shape,  which  are  maintained  apart  by  their 
albuminous  coatings. 

C.  To  some  oil  add  a  little  of  the  free  fatty  acids  ob- 
tained in  Exercise  14,  and  then  a  few  drops  of  a  strong 
solution  of  sodium  carbonate.  Shake  well,  and  a  stable 
emulsion  is  produced. 

This  experiment  shows  that  the  presence  of  free  fatty 
acids  is  probably  necessary  in    producing  an  emulsion. 

It  is  probable  that  the  alkaline  juices  of  the  intestine 
act  in  this  way  by  splitting  up  the  fats  into  free  acids 
and  glycerin. 

Exercise  16.  Crystallization  of  Fats. 

A.  Examine  a  little  tallow,  without  melting  it,  under 
the  microscope  and  note  the  gratmles. 

B.  Melt  the  tallow,  place  a  drop  of  it  on  a  glass  slide, 
press  down  a  cover  glass  on  it  before  it  is  hard,  let  cool, 


532  DENTAL   CHEMISTRY. 

and  then  examine  with  the  microscope.     Note  that  crys- 
tals have  now  formed.* 

These  experiments  show  that  fats  in  the  tissues  have 
no  crystalline  structure,  but  that,  after  being  melted,  they 
become  crystalline  on  standing. 

C.  Dissolve  tallow  in  chloroform,  place  a  drop  on  a 
slide,  let  evaporate  until  film  is  seen  on  top  of  drop, 
put  on  cover  glass,  and  let  stand  until  crystallization  is 
complete.  The  crystals  formed  are  finer  than  those  seen 
in  B. 

It  is  not,  however,  thought  to  be  possible  to  identify  the 
various  fats  by  their  crystalline  forms,  since  from  one  and 
the  same  portion  of  fat,  dissolved  in  chloroform,  four  or 
five  different  kinds  of  crystals  may  be  obtained. 

Exercise  17.  General  characters  of  the 
Proteids. 

A.  Take  several  eggs,  and  having  made  a  small 
hole  in  each  end,  let  the  white  only  escape.  Cut 
up  the  albuminous  fluid,  thus  obtained,  with 
scissors,  so  as  to  divide  the  network  of  mem- 
branes, stir  up  rapidly  with  twice  its  volume  of 
water,  and  strain  through  a  linen  cloth. 

White-of-egg  belongs  to  the  large  number  of  sub- 
stances to  which  the  general  i&rm. protcid  is  given.  (Read 
paragraph  470.  Note  that  the  solution  is  incapable  of 
dialysis,  paragraph  72.) 

B.  Set  a  little  of  the  proteid  solution  aside  in  a 
warm  place  for  a  few  days.  Note  the  odor  and, 
on  addition  of  a  solution  of  lead  acetate  or  nitrate, 
the  blackening.    Putrefaction  has  taken  place. 


*Use  a  power  of  200  to  300  diameters. 


rilVSIOLOGICAL    CHEMISTRY.  533 

Read  paragraphs  471  and  476  and  distinguish  between 
fermentation  and  putrefaction. 

C.  Fill  a  test-tube  two-thirds  full  of  the  solu- 
tion of  white  of  egg  obtained  in  A.  Hold  the 
closed  end  by  the  thumb  and  forefinger,  and  boil 
the  upper  third  over  a  spirit  lamp.  Flocks  appear, 
due  to  formation  of  coagulated  albmnin. 

The  soluble  proteids  (paragraph  472)  are  converted 
into  insoluble  modifications,  by  heating  to  60°  to  70°  C. 
(140°  to  158°  F).  When  once  thus  coagulated,  they  will 
not  return  to  their  original  soluble  form  without  suffering 
some  alteration. 

D.  Procure  the  dried  albumin  (coagulated  blood  al- 
bumin), of  commerce  and  heat  some  of  it  in  an  ignition 
tube.     Note  that  it  is  decomposed. 

E.  Perform  the  experiment  as  in  D,  but  previously  mix 
with  equal  bulk  of  soda-lime  and  heat  strongly. 
Ammoniacal  vapors  are  given  off,  which  may  be  recog- 
nized by  their  odor  or  action  on  litmus  paper.  This 
experiment  may  be  also  tried  with  common  wheat  flour. 

F.  Lastly  subject  the  solution  made  in  A  to  the 
following; — 

/.  Tests  by  acids  and  salts  of  the  heavy  met- 
als'.— 

Add  to  the  solution,  poured  into  seven  test- 
tubes,  solutions  of  the  following  compounds  re- 
spectively:— tannin,  carbolic  acid,  picric  acid, 
acetic  acid  together  with  potassium  ferrocyanide, 
lead  acetate,  mercuric  chloride,  and  silver  nitrate. 
Note  that  a  precipitate  is  formed  in  each  case. 

The  fact  of  the  precipitation  of  &^^  albumin  by  salts  of 
the  heavy  metals  is   taken  into  account  in  the  treatment 


534  DENTAL    CHEMISTRY. 

of  poisoning  by  the  latter.     ( Read  paragraph  232,  Toxi- 
cology). 

2.  XantJio-proteic  rcacUorr. — 

Add  strong  nitric  acid  to  some  of  the  solution 
of  albumin,  boil,  and  a  yellow  precipitate  is  formed, 
or  merely  a  yellow  color  if  the  albumin  solution 
is  dilute.  Now  further  add  ammonia-water, 
when  the  precipitate  will  assume  a  deep  orange- 
red  color.  With  very  dilute  solutions  nothing 
may  happen  on  addition  of  nitric  acid,  but  the 
addition  of  ammonia  produces  a  yellow  color. 

J.  Test  with  Milloiis  reagent: — 

Millon's  reagent  is  made  by  dissolving"  10 
grammes  of  mercury  in  20  grammes  of  nitric 
acid  (sp.gr.  1.42),  and  diluting  with  20  cc.  of 
water. 

(In  dissolving  the  mercury  use  heat  finally,  but  let  cool 
before  diluting  with  water.) 

Add  to  some  of  the  proteid  solution  half  its 
volume  of  Millon's  reagent,  and  heat.  A  yellow- 
ish precipitate  is  formed,  which  becomes  red 
when  boiled.  If  the  solution  is  dilute,  a  red  color, 
without  precipitate  appears. 

4.  Butret  test: — Add  to  the  proteid  solution 
excess  of  sodium  or  potassium  hydroxide,  so  that 
the  reaction  is  strongly  alkaline.  Then  add  two 
or  three  drops  only  of  a  dilute  cupric  sulphate 
solution.  A  violet  color  appears,  which  is  deep- 
ened on  heating. 

5.  Precipitation  by  neutral  salts: — Strongly 


PHYSIOLOGICAL    CHEMISTRY.  535 

acidify  some  of  the  albumin  solution  with  acetic 
acid,  add  some  sodium  sulphate,  and  boil.  A 
whitish  precipitate  takes  place,  except  in  case  of 
peptones.  This  test  is,  therefore,  of  use  in  sep- 
arating peptones  from  other  albuminous  substan- 
ces. Moreover  the  filtrate,  after  boiling,  is  in 
condition  to  be  tested  for  other  substances,  as 
sugar. 

The  term  peptone  is  given  to  the  products  of  the  action 
of  gastric  and  pancreatic  juices  upon  proteids  during  di- 
gestion.    (Paragraph  472.5). 

Exercise  18.    Characteristics  of  individual  proteids* 

A.  Obtain  a  sample  of  albuminous  urine  from  a  patient 
with  Bright's  disease,  and  compare  it  with  the  solution  of 
egg-albumin  prepared  in  exercise  17. 

Note  that  the  reactions  are  the  same.  Now  add  ether 
to  both  the  albuminous  fluids.and  it  will  be  noticed  that  it 
does  not  coagulate  the  albumin  in  the  urine,  but  does,  on 
the  other  hand,  coagulate  that  of  the  ^^%' 

Egg-albumin  differs  from  the  albumin  ot  the  blood,  in 
being  coagulated  by  ether.  Egg-albumin  once  coagulated 
by  heat  is  less  soluble  in  excess  of  strong  nitric  acid  than 
is  blood  albumin.  The  albumin  of  the  blood  is  chiefly  a 
mixture  of  what  is  called  serum-albumin  and  serum-glo- 
bulin. The  fluid  of  hydrocele  also  contains  serum-al- 
bumin. 

Egg  albumin  and  serum  albumin  are  known  as  native 
albumins.     ( Paragraph  472. i ). 

B.  Obtain  fresh  blood  from  the  slaughter-house,  sep- 
arate the  fibrin*  by  whipping  with  twigs,  strain  through 
unsized  muslin,  rotate  in  a  centrifugal  machine,  and  pour 
the  clarified  liquid  thus  obtained  into  a  beaker.     Saturate 

♦Keep  the  fibrin  for  F. 


536  DENTAL    CHEMISTRY. 

with  ammonium  sulphate,  filter,  redissolve  precipitate  in 
water,  saturate  again  with  ammonium  sulphate,  filter, 
wash  with  strong  solution  of  ammonium  sulphate,  dis- 
solve in  a  little  water,  and  place  in  dialyzer.  The  salts 
pass  through  the  membrane,  and  during  dialysis  a  pre- 
cipitate forms  in  the  dialyzer,  which  is  composed  of  a 
proteid  called  serum  globulin.  (Paragraph  472.  2.)  Filter 
the  liquid  after  dialysis.  The  filtrate  is  pure  serum  al- 
burnifi,  and  the  precipitate  remaining  in  the  filter  is  glo- 
bulin. Wash  it  off  with  water  from  the  wash-bottle,  and 
note  its  insolubility  in  water.  Then  add  a  little  salt,  stir, 
and  it  dissolves.  Add  excess  of  salt,  and  it  is  reprecipi- 
tated. 

If  in  the  experiment  above  the  globulin  alone  is  desired, 
it  can  be  prepared  more  quickly,  after  separation  of 
fibrin  and  rotation  in  centrifuge  (removing  blood  corpus- 
cles) by  saturating  the  clarified  liquyl  with  magnesium 
sulphate,  instead  of  ammonium  sulphate.  The  magnes- 
ium salt  precipitates  serum  globulin,  but  not  serum  al- 
bumin. 

The  globulins  are  insoluble  in  pure  water  and  strong 
saline  solutions,  but  soluble  in  weak  saline  solutions. 

The  different  globulins  are  enumerated  in  paragraph 
472,2.  Myosin  is  the  globulin  obtained  by  extracting 
muscle  tissue  in  10  per  cent,  solution  of  ammonium  chlor- 
ide (in  which  it  is  readily  soluble)  and  precipitation  by 
addition  of  large  quantities  of  water.  Myosin  is  a  con- 
stituent of  muscle-plasma,  a  yellowish  opalescent  fluid, 
which  coagulates  after  death,  giving  rise  to  rigof  morth. 

C.  Treat  white  of  ^g,^,  diluted  with  four  times  its  vol- 
ume of  water,  with  one-fifth  its  volume  of  dilute  hydro- 
chloric acid  (0.2  per  cent.)  for  several  hours  at  a  temper- 
ature of  45  C.  (ii3°F.).  Carefully  neutralize  with  solu- 
tion of  an  alkaline  hydroxide,  and  a  precipitate  forms. 


PUVSIOLOGICAL    CHEMISTRY.  537 

It  can  be  washed  in  water  by  decantation.  and  is  no  longer 
coagulated  by  boiling,  when  redissolved  in  hydrochloric 
acid. 

This  experiment  shows  that  the  egg-albumin  (native 
albumin)  which,  as  has  already  been  shown,  is  soluble  in 
water  and  in  neutral  salt  solutions,  has  been  changed  into 
a  form  insoluble  in  these  agents.  This  modified  form  is 
known  as  acid-alhtirnin.  It  is  readily  soluble  in  either 
dilute  acid  or  dilute  alkaline  solutions.  (Read  para- 
graph  472,  4.     See  also  Syntoniti,  472,  2.) 

D.  Remove  the  whites  of  two  fresh  eggs,  divide  freely 
with  scissors,  as  before  in  Exercise  17,  shake  up  well  in  a 
flask,  and  filter  through  linen:  then  add  strong  solution 
of  potassium  hydroxide  until  it  becomes  a  firm  jelly. 
Cut  into  bits,  roll  up  in  gauze,  and  wash  well  in  distilled 
water.  Dissolve  in  boiling  water,  filter,  and  carefully 
neutralize  filtrate  with  acetic  acid.  A  precipitate  now 
takes  place. 

This  experiment  shows  that  the  native  albumin  has 
been  changed  into  a  form  insoluble  in  water  by  contact 
with  the  alkali.  This  modified  form  is  known  as  alkali- 
albumin,  and  is  soluble  in  both  dilute  acid  and  dilute  al- 
kaline solutions. 

The  jelly  formed  by  action  of  the  alkali  is  known  as 
Lieberkuehns  jelly. 

E.  Dilute  100  c.c.  of  fresh  milk  with  400  c.c.  of  water, 
and  add  five  cubic  centimeters  of  acetic  acid,  so  as   to 

.give  it  distinctly  an  acid  reaction.  A  white  precipitate 
takes  place.  Let  settle,  decant,  and  wash  by  decantation. 
Filter,  let  drain,  wash  with  strong  alcohol,  then  with 
ether,  and  let  dry  in  the  air.     Casein  is  obtained. 

Casein  is  the  chief  proteid  of  milk.  It  forms  about  4 
per  cent,  of  cow's  milk,  but  less  than  three  of  human  milk. 
Chemically  it  resembles  alkali-albumin,  being  soluble  in 
weak  alkaline  solutions,  but  differs   from   alkali-albumin 


538  DENTAL    CHEMISTRY. 

in  being  coagulated  by  rennet  (an  enzyme  of  gastric  juice) 
and  in  yielding  no  ash  on  ignition. 

F.  Go  back  to  B  and  wash  with  water  the 
filamentous  coagulum  obtained,  and  then  with 
alcohol  and  with  ether.  An  impure  fibrin  is  ob- 
tained holding  blood  corpuscles.  Note  that  it  is 
insoluble  in  water  and  in  weak  saline  solutions. 
(Read  472,  3). 

G.  Boil  a  solution  of  vvhitc-of-egg  in  water.  Coagulated 
proteid  is  obtained.  Pour  nearly  equal  parts  of  the  mixture 
into  several  test-tubes.  Add  dilute  nitric  acid  to  one, 
strong  nitric  acid  to  another,  dilute  potassium  hy- 
droxide solution  to  a  third,  and  strong  potassium 
hydroxide  to  the  fourth.  It  will  be  seen  that  the  coagu- 
lated proteid  is  soluble  in  strong  acids  and  alkalies  but 
insoluble  in  weak.  It  is  also  insoluble  in  neutral  saline 
solutions. 

Exercise  19.  Digestion  of  Proteids:— 

A.  Take  some  of  the  freshly  prepared  fibrin* 
of  exercise  18,  B.,  cut  it  up  veryfme  in  a  dish, 
and  cover  it  with  5  or  6  times  its  volume  of  weak 
hydrochloric  acid  (0.20  to  0.25  per  cent.).  As 
soon  as  the  fibrin  becomes  transparent,  add  a 
little  glycerin  extract  of  pepsin,  and  warm  the 
whole  to  40°C  ( 104°F)  on  the  water  bath.  At 
the  end  of  half  an  hour  pour  off  half  the  liquid. 
"After  several  hours  the  gelatinous  mass  will 
have  disappeared,  and  an  opalescent  gray  solu- 
tion taken  its  place. 


'Small  pieces  of  boiled  egg  albumin  may  also  be  used. 


PHYSIOLOGICAL    CHEMISTRY.  539 

The  process  which  has  taken  place  is  called  digestion. 
The  essential  constituents  of  the  gastric  juice  are  hydro- 
chloric acid,  in  strength  about  0.25  per  cent.,  and  a  solu- 
ble ferment  {enzyme)  called  pepsin.  Under  the  action  of 
the  gastric  juice  albuminous  substances  suffer  a  profound 
change,  in  virtue  of  which  they  become  soluble  and  ready 
for  absorption,  preliminary  to  nutrition.  The  property 
of  the  gastric  juice  together  also  with  the  pancreatic 
juice,  to  be  spoken  of  further  on,  is  to  convert  other  pro- 
teids  into  bodies  known  as  peptones,  the  latter  being  ex- 
ceedingly soluble,  and  more  or  less  diffusible  through 
animal  membranes.  Peptone  is  the  name  given  to  matter 
completely  digested  by  the  gastric  and  pancreatic  juices. 
Albumose  is  a  term  given  to  substances  in  an  inter- 
mediate stage  between  coagulated  proteid  and  peptone. 
(Paragraph  472,  5). 

So  many  peptic  extracts  are  on  the  market  that  they 
can  be  obtained  at  every  pharmacy,  but,  if  the  student 
has  time,  he  may  prepare  one  himself,  by  separating  the 
mucous  membrane  of  a  hog's  stomach,  cutting  it  into 
small  bits,  placing  in  a  bottle,  and  covering  with  twice  its 
weight  of  good,  strong  glycerin.  Let  stand  a  week  or 
ten  days,  shake  often,  and  pour  off  the  glycerin. 

B.  Test  the  digested  mass  for  the  products  of  di- 
gestion, namely  albumose  and  peptone.  Take  the  liquid 
poured  off  after  half  an  hour  of  digestion,  neutralize  care- 
fully with  ammonia  water,  and  saturate  with  ammonium 
sulphate.  A  precipitate  is  formed  which  is  albumose,  in- 
termediate between  acid  albumin  and  peptone. 

Filter  off  the  albumose  precipitate.  The  filtrate  con- 
tains peptone. 

C.  Test  the  finally  digested  mass  obtained  in  B  as 
follows: — concentrate  by  evaporation  at  low  temperature, 
then  to  the  solution  in  four  test-tubes  add  alcohol,  and 


540  DENTAL    CHEMISTRY. 

solutions  of  tannic  acid,  potassium-mercuric  iodide,  and 
mercuric  chloride.     A  precipitate  forms  in  each  case. 

To  still  another  test-tube  containing  some  of  the  pep- 
tone filtrate  add  solution  of  potassium  or  sodium  hydrox- 
ide till  strongly  alkaline,  then  a  drop  or  two  of  a  very 
dilute  solution  of  cupric  sulphate.  A  pink  color  should 
be  observed. 

To  still  another  portion  in  a  test-tube  add  nitric  acid  : 
no  coagulation  takes  place. 

Exercise  20.  Pancreatic  Digestion:— 

A.  Add  to  100  ex.  of  water  in  a  flask,  0.28 
gramme  of  pancreatin  and  1.5  gramme  of  sodi- 
um bicarbonate.  Shake  up  till  dissolved,  and 
then  add  400  c.c.  of  warmed  fresh  cow's  milk  of 
temperature  38°C  ( 100°F).  Keep  the  mixture  at 
this  temperature  for  half  an  hour.  The  milk  be- 
comes peptonized.  To  a  little  of  it  in  a  test-tube 
add  nitric  acid:  no  coagulation  occurs. 

It  will  be  noticed  from  the  above  experiment  that  pan- 
creatic digestion  goes  on  in  a  solution  which  is  alkaline 
in  reaction,  thus  differing  from  gastric  digestion,  which 
requires  an  acid  medium. 

B.  Final  products  of  pancreatic  digestion: — Go  back  to 
the  freshly  prepared  fibrin  of  Exercise  i8  and  weigh  out 
25  grammes  of  it.  To  this  add  an  equal  weight  of  fresh 
minced  pancreas,  and  250  c.c.  of  water,  to  which  a  little 
thymol  has  been  added. 

Place  all  in  a  flask  and  the  latter  in  a  thermostat,  and 
keep  at  a  temperature  of  40°  C  (104°  F)  for  six  hours. 

At  the  expiration  of  this  time  pour  off  about  one-third 
of  the  mixture,  boil,  and  filter  warm.  Concentrate  the 
filtrate  to   a  small   bulk,  and   examine  drops  under  the 


PHYSIOLOGICAL    CHEMISTRY.  541 

microscope   for  leucin  and  tyrosin   (paragraph  474.  10). 
Leucin  forms  spheres,  tyrosin  long  needles. 

The  remaining  two-thirds  of  the  mixture  is  left  for  six 
hours  longer  in  the  thermostat  at  40°  C,  when  the  char- 
acteristic odor  of  indol  is  developed. 

Exercise  21.  The  Gastric  Juice. 

A.  Obtain  the  gastric  juice  for  examination 
by  use  of  the  stomach-tube*  at  a  time  when 
stomach  is  free  from  food,  as  before  breakfast, 
or  an  hour  or  so  after  a  test  meal  has  been  taken. 
The  meal  usually  consists  of  bread  and  water 
taken  on  an  empty  stomach. 

B.  Take  the  reaction  with  litmus  paper.  Nor- 
mal gastric  juice  reddens  blue  litmus. 

C.  Determine  presence  of  free  acids  by  the 
Congo-red  test  as  follows: — 

Soak  filter  paper  in  a  1  per  cent,  aqueous  solu- 
tion of  Congo-red,  and  let  dry.  If  a  drop  of  the 
juice  is  placed  upon  the  paper,  and  a  blue  color 
appears,  the  presence  of  free  acids  is  indicated; 
intense  blue  indicates  free  hydrochloric  acid. 

D.  Determine  the  total  acidity :  To  10  c.c. 
of  the  gastric  filtrate  add  a  few  drops  of  phenol- 
phtalein  solution,  and  then  run  in  slowly  deci- 
normal  potassium  hydroxide  solution,t  until 
the  liquid  assumes  a  slight  reddish  tint,  which 
does  not  disappear  with  stirring.  Express  the 
percentage  of  acidity  in  terms  of  c.c.  of  hydrox- 

♦For  complete  description  see  Ewald  on  "Diseases  ot  the   Stomach."  D.   Apple 
ton  &  Co.,  New  York. 

fThis  solution  can  be  obtained  of  any  large  dealer  in  chemicals. 


542  DENTAL    CHEMISTRY. 

ide  used;  thus,  if  50  c.c.  of  deci-normal  potas- 
sium hydroxide  are  necessary  for  neutralization, 
express  the  acidity  as  50  per  cent. 

E.  Determine  the  presence  of  free  hydro- 
chloric acid: — 

1.  Methyl-Violet  test.  Make  an  aqueous  solu- 
tion of  methyl-violet,  and  dilute  it^  until  it  has  a 
reddish-violet  color.  Mix  with  the  gastric  filtrate, 
and  a  blue  color  results  if  free  hydrochloric  acid 
is  present. 

2.  Phloroglucin  and  Vanillin  test.  Dissolve 
2  grammes  phloroglucin  and  1  gramme  vanillin 
in  30  a.a.^  of  absolute  alcohol.  Keep  in  a  dark 
bottle.  Mix  5  c.c.  of  this  solution  with  an 
equal  volume  of  the  gastric  juice,  and  concen- 
trate on  the  water-bath.  If  free  hydrochloric 
acid  is  present,  the  liquid,  as  it  becomes  concen- 
trated, turns  red. 

3.  00-Tropaolin  test.  Soak  filter  paper  in  a 
saturated  solution  of  00-Tropaolin  and  let  dry. 
Moisten  the  paper  with  a  drop  of  the  filtrate, 
then  place  the  paper  in  a  watch-glass,  and  heat. 
If  there  is  free  hydrochloric  acid,  the  paper  first 
becomes  brown,  then,  as  it  dries,  lilac. 

Note: — It  is  said  that  none  of  these  color  tests  give  en- 
tirely reliable  conclusions. 

In  cases  where  the  reaction  is  positively  obtained,  free 
hydrochloric  acid  is  undoubtedly  present;  but  the  re- 
action sometimes  fails  from  presence  of  albumin,  peptone, 

*Jaksch  uses  loo  c.c.  of  alcohol. 


PHYSIOLOGICAL    CHEMISTRY.  543 

or  salts,  even  when  tree  hydrochloric  acid  is  present  also. 
The  reactions  with  methyl-aniline,  congo-red,  and  benzo- 
purpurin  are  thought  by  Von  Jaksch  to  be  most  reliable* 
Ewald  thinks  well  of  the  phloroglucin-vanillin  test. 

4.  Benzo-purpurin  test:— Soak  strips  of  filter 
paper  in  a  saturated  solution  of  benzo-purpurin, 
6.  B.  Let  dry.  Filter  the  gastric  contents,  and 
immerse  the  dried  paper  in  the  filtrate.  If  a 
brownish-black  color  results,  organic  acids  (lactic 
or  butyric)  are  present,  with  or  without  hydro- 
chloric acid.  If  a  blue  color  results,  hydrochloric 
acid  is  present.  Shake  the  brown  or  black  paper 
in  ether  and,  if  the  brown  color  changes  to  blue, 
hydrochloric  acid  is  present.  If  it  fades  out 
without  turning  blue,  organic  acids  are  present. 

F.  Deterniine  presence  of  organic  acids,  as 
lactic,  by  Uffelmann's  reagent: — dissolve  1 
gramme  of  pure  carbolic  acid  in  75  c.c.  of  water. 
To  this  add  5  drops  of  a  strong  solution  of  ferric 
chloride,  which  produces  a  deep  blue  color.  Of 
this  solution,  thus  made,  take  5  c-.c.  and  add  to  it 
a  few  drops  of  the  gastric  filtrate.  If  lactic  acid  is 
present,  the  color  changes  from  blue  to  yellow. 

Dr.  Long  remarks  that  weak,  almost  colorless  solution 
of  ferric  chloride  alone  serves  as  a  test  solution,  as  its 
color  becomes  much  deeper  on  addition  of  a  trace  of 
lactic  acid. 

Professor  Simon  recommends  in  doubtful  cases  shaking 
10  c.  c.  of  gastric  filtrate  with  50  c.  c.  of  ether,  evaporating 
ethereal  solution  to  dryness,  dissolving  the  residue  in  a  few 
drops  of  water,  then  adding  Uffelmann's  reagent  as  above. 


544  DENTAL    CHEMISTRY. 

G.  Estimate  the  amount  of  free  hydrochloric 
acid,  approximately,  by  use  of  the  phloroglucin- 
vanillin  reagent: — the  more  or  less  intense  red 
color  gives  us  a  rough  idea  of  the  larger  or  smaller 
amount  of  free  acid  present.  More  accurately 
dilute  the  gastric  juice,  giving  the  phloroglucin- 
vanillin  reaction  with  water,  and  test  repeatedly, 
noting  at  what  stage  of  dilution  the  test  fails. 
If  the  red  color  is  just  visible  with  the  20th  di- 
lution with  equal  parts  water,  then  the  juice  con- 
tains 0.1  per  cent,  of  free  hydrochloric  acid,  since 
the  limit  of  the  reaction  is  known  to  be  1  -20,000'- 

H.  Boass  cancer  test. 

This  test  depends  on  absence  of  HCl  and'pxQS- 
ence  of  lactic  acid.  Preliminary  lavage  and  use 
of  oat-meal  gruel  given  after  lavage  are  important. 

According  to  Rosenheim  in  12  to  15  per  cent, 
of  all  cases  of  cancer  of  the  stomach  no  diagnosis 
is  possible. 

Long  thread-like  bacilli,  immobile,  and  often 
occuring  in  enormous  numbers  have  been  found 
in  stagnating  stomach  contents,  when  HCl  is  ab- 
sent and  large  quantities  of  lactic  acid  present. 
Sarcinse  are  very  rarely  seen  in  the  above-des- 
cribed stomach  contents.  Sulphuretted  hydro- 
gen is  not  found  in  cancer.  Absence  of  pepsin 
as  an  important  symptom  is  disputed.  Tumors 
on  the  anterior  wall  have  been  recognized  with 
the  gastrodiaphone. 

•Ewald. 


PHYSIOLOGICAL    CHEMISTRY.  545 

Exercise  22.   The  blood. 

A.  Obtain  some  fresh  blood  and  take  the  spe- 
cific gravity  and  the  reaction.  Note  that  the 
former  lies  between  1045  and  1075,  and  that  the 
reaction  is  alkaline,  shown  by  putting  a  few 
drops  on  plaster  of  Paris  surface  which  has 
been  soaked  in  neutral  litmus. 

B.  Heat  blood  diluted  with,  say,  20  times 
its  volume  of  water,  and  note  that  the  red 
color  is  mostly  destroyed  near  the  boiling 
point,  hemoglobin  being  resolved  into  brown 
hematin  and  albumin. 

C.  Evaporate  a  drop  of  blood  on  a  glass 
slide,  add  a  couple  of  drops  of  glacial  acetic 
acid,  and  boil.  Put  on  a  cover  glass,  let  cool, 
and  examine  with  high  power  of  microscope 
for  the  dark-brown,  prisms  or  plates  called 
Teichmann's  crystals  (hemin). 

D.  Obtain  an  old  blood  stain  on  linen,  treat 
with  a  very  little  distilled  water,  then  exam- 
ine as  in  C,  except  that  a  small  crystal  of 
sodium  chloride  must  be  added  to  the  glacial 
acetic  acid  in  order  to  furnish  hydrochloric  acid, 
hemin  being  a  chloride  of  hematin. 

E.  Mix  old  spirit  of  turpentine  or  ethereal 
solution  of  hydrogen  dioxide  and  fresh  tincture 
of  guaiacum,  equal  parts,  and  let  the  blood  solu- 
tion of  B  trickle  down  into  the  mixture  in  quan- 
tity equal  to  that  of  the  latter.  A  blue  zone  is 
seen  at  the  juncture  of  the  blood  and  mixture, 


546  DENTAL    CHEMISTRY. 

due  to  oxidation  of  the  guaiacum  resin  by  the 
turpentine  or  dioxide  in  presence  of  the  blood. 

F.  Pass  a  current  of  ordinary  illuminating  gas 
from  the  gas  jet  into  a  test-tube  half  full  of  de- 
fibrinated  blood,  for  a  short  time.  Cover  the 
mouth  oi»  the  tube  with  the  thumb,  shake 
thoroughly  and  then  pass  more  gas  into  the  blood. 
The  color  changes  to  cherry  red,  the  arterial  red 
having  disappeared,  owing  to  a  compound  formed 
by  union  of  the  carbon  monoxide  in  the  gas  with 
the  hemaglobin  of  the  blood. 

G.  Shake  the  tube  in  contact  wit^h  the  air 
and  note  persistence  of  the  darker  red  color. 

These  last  two  experiments  show  what  happens  in  the 
blood  when  poisoning  by  illuminating  gas  takes  place. 


ANALYSIS   OF   SALIVA,   TEETH,   ETC.  54'Jf 


CHAPTER  IX. 

ANALYSIS    OF    SALIVA,    TEETH,    TARTAR,    AND   URINE. 

570.  A  complete  course  in  salivary  analysis  is  as 
essential  to  the  dental  student  as  one  in  urinary  analysis 
to  the  medical  student. 

I.  Become  familiar  with  the  physical  char- 
acteristics of  the  saHva:  i.  Cause  the  pa- 
tient to  wash  his  mouth  out  thoroughly  with 
a  warm,  dilute  solution  of  sodium  bicarbonate, 
and  afterwards  with  cold  spring  water,  if  it  can 
be  obtained,  or  with  cold  distilled  water. 
Brush  the  inside  of  the  mouth  lightly  with  a 
glass  rod,  moistened  with  a  little  dilute  acid, 
when  the  mouth  will  be  filled  with  a  consider- 
able amount  of  clear,  viscid  fluid.  Cause  the 
patient  to  expectorate  into  a  cylindrical  glass 
vessel,  tapering  at  the  bottom  and  provided 
with  a  lip,  so  that  the"  sediment  may  be  col- 
lected and  examined  with  the  microscope. 

II.  While  it  is  settling,  note  the  color,  odor, 
reaction,  transparency,  consistence,  appear- 
ance of  sediment,  specific   gravity:     color 


548  DENTAL   CHEMISTRY. 

should  be  absent,  so  also  odor;  take  the  reac- 
tion with  litmus  paper,  dipping-  both  red  and 
blue  slips  into  the  fluid  at  once;  if  neither 
change  color,  the  reaction  is  neutral;  if  the 
blue  is  turned  red,  the  reaction  is  acid;  if  the 
red  is  turned  blue,  the  reaction  is  alkaline.  A 
variety  of  litmus  paper  may  now  be  obtained, 
which  turns  red  in  an  acid  liquid,  and  blue  in 
an  alkaline  one.  The  transparency  should  not 
be  great,  for  normal  saliva  is  turbid;  the  con- 
sistence should  be  glairy,  viscid,  and  there 
should  be  froth.  Notice  whether  the  sediment 
after  standing  some  hours  is  opaque  and  whit- 
ish, or  whether  stringy  masses  are  present  in  it. 
[The  latter  is  not  likely  to  be  the  case  in  saliva 
obtained  as  directed  in  (i)  but  is  sometimes 
noticed  in  cases  of  chronic  gastric  catarrh]. 

N.  B.  In  order  to  note  the  physical  charac- 
ters in  detail,  to  collect  and  examine  the  sedi- 
ment, and  to  ascertain  the  specific  gravity, 
several  specimens  of  saliva  collected  in  separate 
beakers  or  cylinders  should  be  conveniently 
procured,  in  order  to  save  time.  The  first  speci- 
men may  be  set  aside,  in  order  that  the  sediment 
may  settle  in  it;  the  second  specimen  may  be 
used  for  observation  of  the  color,  odor,  reaction, 
and  also  for  the  chemical  tests ;  the  third,  in  case 
of  a  scanty  supply,  may  be  set  aside  for  dilu- 
tion in  order  to  ascertain  the  specific  gravity 
by  methods  hereafter  to  be  explained. 

III.      Next  ascertain    the  specific    gravity, 


ANALYSIS   OF   SALIVA,   TEETH,   ETC,  549 

which  can  be  done  by  means  of  the  urinome- 
ter: 

The  urinometer  consists  of  a  g-lass  float 
weighted  below  with  a  bulb  of  mercury,  and 
with  a  stem  graduated  from  o  to  60  at  intervals 
of  one  or  two  degrees;  the  instrument  should 
sink  to  zero  when  floated  in  distilled  wafer  in 
the  beaker,  which  usually  accompanies  it.  If 
there  is  plenty  of  saliva,  the  specific  gravity  can 
be  obtained  at  once  by  floating  the  urinometer 
in  the  saliva,  and  reading  off  the  number  on 
the  scale  at  the  level  of  the  liquid.  It  should 
average  from  1002  to  1006,  or  possibly,  1008  or 
9.  If  the  amount  of  saliva  is  scanty,  the  spe- 
cific gravity  may  be  obtained  by  dilution:  take 
one  part  of  saliva  by  volume  (bulk),  and  add 
one  part  of  distilled  water  to  it  so  as  to  make 
enough  liquid  to  fill  the  cylinder,  or  beaker 
used,  say  two-thirds  full;  take  the  specific 
gravity  as  before  and  multiply  the  last  figure 
of  it  by  2,  and  the  result  is  the  true  specific 
gravity  of  the  saliva. 

IV.  Next  proceed  with  chemical  tests,  first 
for  the  normal  constituents,  next  for  possible 
abnormal  ones. 

571.  A.  Qualitative  tests  for  normal  con- 
stituents.— • 

I.  Boil  a  little  of  the  saliva  in  a  slender, 
long  test-tube,  held  between  thumb  and  fore- 
finger by  the  closed  end;  heat  the  upper  part 


550  DENTAL   CHEMISTRY. 

only  of  the  fluid.     A  turbidity  noticed  indicates 
presence  of  albumin. 

2.  To  a  fresh  supply  of  the  saliva,  add  a  drop 
or  two  of  ferric  chloride:  a  blood-red  color  in- 
dicates presence  of  sulphocyanide.  This  test 
is  sometimes  performed  by  means  of  prepared 
test-paper:  immerse  strips  of  paper  in  an  am- 
ber-colored solution  of  ferric  chloride,  to  which 
a  few  drops  of  hydrochloric  acid  have  been 
added.  Let  dry.  A  drop  of  saliva  will  give  a 
red  spot  on  such  paper.  The  red  color  is  re- 
moved by  addition  of  a  drop  of  mercuric  chlor- 
ide. 

[The  test  may  fail  altogether,  in  which  case  the  saliva 
must  be  distilled  with  phosphoric  acid  and  the  first  of  the 
distillate  tested]. 

3.  Collect  a  plentiful  supply  of  the  saliva  by 
chewing"  rubber,  or  by  inhaling  ether  vapor 
into  the  mouth:  add  four  times  its  volume  of 
water,  stir  well,  let  settle,  pour  off  the  super- 
natant liquid  from  the  sediment.  Prepare 
some  starch  mucilage  by  rubbing  a  little  starch 
into  a  thin  paste,  with  a  little  cold  water,  then 
pouring  into  about  half  a  pint  of  boiling  water. 
Boil  for  five  or  ten  minutes  and  when  cool,  de- 
cant the  clear  liguid.  Pour  some  of  the  starch 
mucilage  into  a  small  beaker,  add  a  little  of 
the  diluted  saliva,  lay  aside  for  ten  minutes  in 
a  drying  oven  where  the  temperature  is  about 
95°  to  104°;  in  default  of  a  hot  chamber,  place 


ANALYSIS   OF    SALIVA,  TEETH,    ETC.  55X 

the  beaker  some  time  in  water  of  temperature 
of  104°,  or  warm  the  mixture  very  gently  in  a 
test-tube  over  a  flame,  taking  care  by  coohng 
with  the  hand  that  the  temperature  does  not 
rise  much  above  95°.  Apply  the  tests  for 
starch  and  for  sugar,  and  it  will  be  found  that 
the  starch  has  disappeared  wholly  or  in  part, 
and  that  sugar  has  been  formed,  showing  pres- 
ence of  diastatic  ferment  (ptyalin)  in  saliva. 

[The  test  for  sugar  should  be  made  as  follows:  procure 
what  is  known  as  Fehling's  test-liquid,  essentially  an 
alkaline  solution  of  copper  sulphate,  boil  a  little  of  it 
diluted  with  four  parts  of  water  in  a  test-tube,  and  if  it 
does  not  lose  its  blue  color  on  cooling  it  is  fit  for  use. 
Now  add  a  drop  or  two  of  the  starch  mucilage  on  which 
the  saliva  has  acted,  and  raise  just  to  boiling  point  again; 
reddisk-ycllozv  precipitate  indicates  presence  of  grape-sugar. 
Compare  now  the  action  of  a  weak  solution  of  iodine  in 
alcohol  on  the  original  starch  mucilage,  and  on  that 
which  has  been  acted  on  by  the  saliva;  with  the  orig- 
inal it  should  form  a  deep  indigo-blue  compound]. 

4.  Fill  a  tall  beaker  with  dilute  acetic  acid 
— say  one  part  of  the  ordinary  acid  to  two  or 
three  of  water — and  let  the  saliva  drop  slowly 
into  it;  stringy  flakes  indicate  presence  of 
mucin. 

5.  To  show  the  inorganic  acids,  evaporate 
the  saliva  to  dryness  in  a  porcelain  crucible; 
do  not  withdraw  the  heat  till  the  residue  is 
well  blackened  or  darkened  from  charring  of 
the  organic  matter;  when  it  is  so,  remove,  let 


552  DENTAL   CHF.MISTRY. 

cool,  and  add  a  little  distilled  water,  stirring 
well,  and  adding  a  drop  of  acetic  acid.  Filter 
and  divide  the  filtrate  into  three  parts;  to  two 
add  a  few  drops  of  nitric  acid,  and  to  one  a 
solution  of  silver  nitrate;  a  turbidity  indicates 
presence  of  chlorides.  The  precipitate  thus 
formed  should  be  soluble  in  ammonia.  To  the 
other  add  ammonium  molybdate  solution  and 
heat;  a  yellowish  color,  becoming"  possibly  a 
precipitate,  indicates  presence  of  phosphates. 
To  the  third  add  a  drop  or  two  of  hydrochloric 
acid  and  some"  barium  chloride  solution;  a 
white  precipitate  shows  presence  of  sulphates. 
6.  To  show  the  presence  of  lime  and  mag- 
nesia, take  a  portion  of  the  filtrate  obtained  in 
5,.and  divide  it  into  two  parts;  to  the  first  add 
ammonium  oxalate  solution:  a  white  precipi- 
tate indicates  presence  of  calcittm  (lime);  to 
the  second  part  add  ammonia  and  sodium 
phosphate  solution:  a  white  precipitate  indi- 
cates presence  of  magnesium.  The  calcium 
precipitate  should  be  insoluble  in  acetic  acid 
but  soluble  in  nitric;  the  magnesium  precipi- 
tate should  dissolve  completely  in  ^acetic  acid 
on  shaking. 

572.    B.    Quantitatiye  analysis. — 

Ptyalin  may  be  separated  nearly  pure  by  precipitating 
fresh  saliva  with  dilute  normal  phosphoric  acid  and  then 
adding  lime-water;  filter  off  precipitate  and  dissolve  it  in 
distilled   water,  from  which    it    is  to    be    precipitated  by 


ANALYSIS   OF   SALIVA,  TEETH,   ETC.  553 

alcohol,  collected  on  a  filter,  washed  repeatedly  with  a 
mixture  of  alcohol  and  water,  dried,  and  weighed.* 

Mucin,  obtained  as  in  the  qualitative  method,  can  be  col- 
lected on  a  filter,  washed  with  alcohol,  dried,  and  weighed. 
The  weight  of  the  saliva  being  known,  the  percentage  of 
ptyalin,  or  of  mucin,  can  be  readily  calculated  by  dividing 
each  weight  by  the  weight  of  the  entire  saliva  used. 

Fatty  matters  can  be  estimated  as  follows:  a  definite 
quantity  of  saliva  being  evaporated  to  dryness  over  the 
water-bath,  triturate  the  residue  carefully,  scraping  off 
any  that  may  adhere,  and  exhaust  thoroughly  with  boil- 
ing ether.  Evaporate  in  a  weighed  platinum  capsule  f 
and  the  increase  in  weight  of  the  capsule  represents  the 
amount  of  fatty  matter  present.  The  operation  should  be 
repeated  often  enough,  to  obtain  a  reasonably  constant 
result. 

Potassium  Sulphocyanide.  Dissolve  perfectly  dry 
potassic  sulphocyanide,  0.05  gram  in  water  ( lOO  C.  c),  and 
add  to  it  ferric  chloride  till  no  more  intensity  of  color  is 
produced;  then  measure  the  volume  of  liquid.  This  is 
the  test  solution  a. 

Now  take  a  definite  volume  of  the  saliva,  and  place  it  in 
a  small,  graduated,  cylindrical  glass  vessel;  add  to  it  a 
drpp  or  two  of  hydrochloric  acid  and  ferric  chloride,  with 
brisk  stirring,  until  its  maximum  of  intensity  of  color  is 
obtained;  call  this  b. 

Having  carefully  noted  the  intensity  of  the  tint  b,  place 
three  or  four  cylinders  similar  to  that  holding  the  saliva 
beside  it  on  a  piece  of  white  paper  in  a  good  light;  then 
add  to  one  of  these  by  means  of  a  graduated  pipette  a  few 
C.  c.  of  the  ferric  sulphocyanide  solution  {a);    make  it  up 

*  In  order  to  dry  properly  there  is  need  of  a  drying  oven  ;  filters 
are  conveniently  dried  and  weighed  by  placing  them  between  two 
watch  glasses  held  together  by  a  clamp.  For  weighing  there  is  need 
of  a  delicate  c/iemical  balance. 

I  A  nickel  crucible  may  be  used  for  this  operation. 


554  DENTAL    CHEMISTRY. 

to  the  same  volume  as  the  saliva  (b)  using  distilled  water. 
After  stirring  well  note  the  intensity  of  color  by  looking 
vertically  downwards  through  the  column  of  liquid,  and 
compare  it  with  that  of  the  saliva.  If  not  so  deep  a  red 
tint,  a  fresh  experiment  must  be  made  in  the  same  way, 
but  using  more  of  the  sulphocyanide  test  solution.  We 
thus  proceed  till  an  equal  intensity  of  color  is  obtained  in 
the  two  columns  of  liquid.  From  the  amount  of  the  test 
solution  a  required,  we  can  easily  calculate  the  percentage 
of  sulphocyanide  in  the  saliva.     (Charles). 

Each  C.  c.  of  the  test  solution  {a)  contains  .0005  grams 
sulphocyanide.  If,  therefore,  10  C.  c.  of  the  test  solution 
are  required,  the  amount  of  sulpl1t)cyanide  in  the  saliva  is 
.0005  X  10  or  .005,  and  so  on.  Divide  the  amount  of 
sulphocyanide  found  by  the  weight  of  the  saliva,  and  the 
quotient  is  the  percentage  of  sulphocyanide. 

The  chlorides  may  be  estimated  iwliimctrically,*  that  is 
by  use  of  standard  solutions,  directly  from  the  saliva  after 
the  removal  of  the  organic  constituents.  Fifty  cubic 
centimetres  of  saliva  should  be  boiled  and  filtered.  To 
the  filtrate  add  an  equal  volume  of  saturated  baryta  solu- 
tion ( I  volume  barium  nitrate,  2  volumes  barium  hydrate,, 
each  a  saturated  solution);  this  precipitates  the  organic 
constituents  and  phosphates.  Filter,  and  to  the  filtrate 
add,  drop  by  drop,  a  standard  solution  of  mercuric  nitrate, 
of  which  I  C.c.  precipitates  .01  gram  of  sodium  chloride. 
The  number  of  C.c,  used  shows  the  number  of  iJoths  of  a 
gram  of  sodium  chloride  present.  The  filtrate  from  the 
baryta  precipitate  should  be  acidulated  with  a  few  drops 
of  nitric  acid,  before  the  mercuric  nitrate  is  added. 

*In  volumetric  analysis  the  determination  is  in  general  brought 
about  by  adding  to  a  weighed  quantity  of  the  substance  to  be  ex- 
amined a  solution  of  some  reagent  of  known  strength,  until  the  reac- 
tion is  exactly  completed.  The  operation  is  termed  titration,  and  re- 
quires skill  and  practice.  The  student  is  referred  to  "  Sutton's  Vol- 
umetric Analysis." 


ANALYSIS   OF   SALIVA,   TEETH,    ETC.  555 

573     Special  tests  for  constituents  of  oral  secretions : 

T.  Storer  How  has  arranged  a  series  of  litmus  tests  of 
oral  fluids  together  with  a  system  of  nomenclature  as  fol- 
lows: first  take  with  the  foil-pliers  a  piece  of  blue  litmus, 
wet  it  with  parotid  saliva  and  put  the  wet  piece  on  a  leaf 
from  a  foil  book.  In  like  manner  treat  the  sub-max. 
saliva,  placing  the  wet  piece  on  the  leaf  below  the 
other.  Thus  also  test  between  the  teeth,  in  carious 
cavities,  pulp  cavities,  roots,  sulci,  pus-pockets,  under  cal- 
culi, plates,  bridges,  etc.  Make  the  same  tests  in  the  same 
order  with  red  litmus.  Fill  up  the  blank  with  the  other 
statistics,  and  then  note  and  record  either  the  unchanged 
color  of  both  the  blue  and  the  red  by  the  symbol  N,  neu- 
tral, or  the  change  of  the  blue  to  red  by  the  symbol  A 
acid;  or  the  change  of  the  red  to  blue  by  the  symbol  Aj 
alkaline,  as  the  case  may  be. 

As  abbreviations  for  the  different  reactions,  How  sug- 
gests the  following: 

A.  — Alkaline. 

A  —Acid. 

N  — Neutral. 

I    — Slightly,  alkaline  or  acid. 

L  — Obviously,  alkaline  or  acid. 

U  — Decidedly,  alkaline  or  acid. 

0  — Excessively,  alkaline  or  acid. 

[Dr.  Oliver,  of  England,  has  prepared  for  use  in  urinary 
analysis,  litmus  paper  charged  with  a  definite  quantity  of 
alkali  so  as  to  distinguish  several  grades  of  acidity  in  re- 
action, such  as  siib-acid,  acid,  hyper-acid,  etc.  It  would 
seem  as  if  these  papers  under  certain  circumstances  might 
be  of  use  in  salivary  analysis]. 

Detection  of  mercury  in  saliva:  collect  all  the  saliva 
possible  in  24  hours,  and  acidulate  it  with  dilute  hydro- 
chloric acid  (i  part  acid  to  9  of  water).  The  mixture  is 
heated  for  two  hours  on  a  water  bath,  filtered,  and  filtrate 
marked  {a'),  and  concentrated  to  half  its  bulk  over  the 


556  DENTAL   CHEMISTRY. 

water  bath.  Go  back  to  the  precipitate  on  the  filter,  place 
it  in  a  beaker  filled  three  parts  full  with  dilute  hydro- 
chloric acid  (i  part  acid  to  6  parts  water),  and  heat  the 
whole  over  a  water  bath,  adding  from  time  to  time  small 
quantities  of  potassium  chlorate,  and  constantly  stirring 
to  dissolve  the  organic  residue.  When  this  is  completely 
dissolved,  filter,  and  add  filtrate  to  the  previous  filtrate 
marked  a.  Concentrate  the  mixed  filtrates  to  one-fourth 
their  bulk.  The  solution  contains  as  dichloride,  any  mer- 
cury that  may  be  present.  To  prove  the  presence  of 
mercury,  (i)  place  a  drop  of  the  solution  on  a  gold  or 
copper  coin,  and  touch  with  blade  of  knife;  a  bright,  sil- 
very stain  will  appear.  (2)  Place  a  few  strips  of  pure 
copper-foil  in  a  test-tube,  and  add  a  little  of  the  solution, 
and  boil;  the  mercury  will  be  deposited  on  the  surface  of 
the  copper-foil.  Remove  the  strips  and  wash  them  with 
very  dilute  solution  of  ammonia,  and  dry  them  between 
blotting-paper.  Then  place  them  at  the  bottom  of  a  nar- 
row glass  tube  (German  glass),  and  apply  heat;  the  mer- 
cury will  be  volatilized,  and  deposited  as  a  ring  of  minute 
globules  at  the  upper  end  of  the  tube.  The  character  of 
these  globules  can  generally  be  recognized  by  the  eye. 
If,  however,  they  are  too  small,  remove  the  strips  of  cop- 
per from  the  tube,  and  dissolve  the  ring  by  the  addition 
of  a  drop  or  so  of  dilute  nitro-muriatic  acid,  and  gently 
evaporate  the  solution.  Dissolve  the  residue  in  a  little 
water,  and  divide  into  two  equal  portions:  («)  tested  with 
a  drop  of  dilute  solution  of  potassium  iodide,  it  gives  a 
red  precipitate  of  mercuric  iodide,  soluble  in  excess  of 
potassium  iodide  solution;  {b)  a  drop  added  to  solution 
of  caustic  potash  gives  a  yellow  precipitate  of  hydrated 
mercuric  oxide,  insoluble  in  excess  of  liquor  potassas. 
(Ralfe). 

Microscopic  examination  of  tlie  sediment:  let  the 
saliva  settle  in  a  conical  vessel  as  directed,  and  examine 
the  sediment  with  a  power  of  400  to  500  diameters;  note 


ANALYSIS   OF   SALIVA,   TEETH,   ETC. 


557 


the  salivary  corpuscles,  various  kinds  of  epithelial  cells. 
With  higher  powers  bacteria,  fungi,  etc.,  may  be  studied. 
574.  Morphology  of  the  human  sputum :  E.  Cutter 
has  made  a  partial  list  of  the  forms  and  substances  found 
in  the  human  sputum. 


1.  Mucous  corpuscles. 

2.  Mucous  cells  swarming  with 

the  moving  spores,  probably 
of  the  leptothrix  buccalis; 
not  found  in  the  mouths  of 
healthy  infants. 

3.  Mucous  corpuscles  distended 

with  crystalline  and  other 
bodies. 

4.  Epithelia,  ciliate  and  non-cili- 

ate. 

5.  Spirillum. 

6.  Vibriones. 

7.  Micrococcus  spores. 

8.  Bacilli. 

9.  Spirulina  splendens. 

10.  Gemiasmaverdans  and  rubra. 

11.  Alcoholic  and  lactic  acid  alco- 

holic yeast. 

12.  Vinegar  yeast  and  lactic  acid 

vinegar  yeast. 

13.  Mycelial  filaments  of  vinegar 

and  lactic  acid  yeasts. 

14.  Leptothrix    buccalis     spores 

and  filaments. 

15.  Papillae    of    tongue,    usually 

infiltrated  with  spores  of  14. 

16.  Mucor  malignans. 

17.  Hairs  of  plants  and  animals. 

18.  Vegetations  found  in  croupal 

membranes. 

19.  Pus  corpuscles. 

20.  Blood  corpuscles,  white   and 

red. 

21.  Clots  of  blood. 

22.  Granular  tubercular  masses. 

23.  Elastic  lung-fibres. 


33. 
34. 


35. 


24.  Inelastic  lung-fibres. 

25.  Lumen  of  veins  and  arteries. 

26.  Carbonized  tissue  from  lungs. 

27.  Partially  carbonized  vegeta- 

ble tissues  from  smoke. 

28.  Oxalate  of  lime. 

29.  Uric  acid  crystals. 

30.  Cystine. 

31.  Phosphate  of  lime. 

32.  Triple  phosphate. 
Cholesterine. 
Calculi,  made  up  of  one  or 

more  of  28,  29,  30,  31,  32,  33. 
These  may  all  come  under 
the  appellation  of  "gravel  of 
the  lungs." 

Other  crystals  whose- names 
have  not  been  made  out. 
36.  Amorphous,  organic,  and  in- 
organic matters,  including 
dust  and  dirt  inhaled  from 
the  atmosphere. 

Portions  of  feathers  of  ani- 
mals and  insects. 

Potato  starch. 

39.  Wheatstarch. 

40.  Elements     of    animal    food 

eaten,  cookedand  uncooked. 

41.  Elements  of  vegetable  food 

eaten, cooked  and  uncooked. 

42.  Cotton  fibre. 

43.  Silk  fibre. 

44.  Linen  fibre. 

45.  Wool  fibre. 

46.  Woody  fibres,pittedducts,etc. 

47.  Asthmatos  ciliaris. 


37. 


38. 


558  DENTAL   CHEMISTRY. 

575.    Analysis  of  teeth  and  tartar:— 

I.  Qualitative  analysis  of  the  teeth. 

1.  To  show  the  presence  of  organic  mat- 
ter, ossein,  etc.  Digest  the  teeth  for  a  day  or 
two  in  dilute  hydrochloric  acid  (10  per  cent). 
The  earthy  salts  will  be  dissolved  out,  and 
what  remains  will  be  soft  and  elastic. 

2.  To  show  the  earthy  salts:  place  a  few 
teeth  in  a  clear  fire  and  let  them  remain  there 
until  perfectly  white.  Powder,  and  dissolve  in 
hydrochloric  acid;  dilute  and  add  plenty  of 
ammonia;  a  white,  gelatinous  precipitate  oc- 
curs of  phosphates  of  lime  and  inagjiesia. 
Filter,  and  to  the  filtrate  add  oxalate  of  am- 
monium: a  precipitate  of  oxalate  of  calciimi 
shows  itself,  indicating  presence  of  lime  not  as 
phosphate;  prove  that  there  is  carbonate  by 
digesting  powdered,  uncalcined  teeth  in  dilute 
hydrochloric  acid,  when  an  effervescence  due  to 
carbonic  anhydride  takes  place. 

II.  Quantitative  analysis  of  teeth:  the  teeth  should  be 
cleaned  and  reduced  to  powder  in  a  mortar;  weigh  out  5 
to  10  grams  of  powdered  teeth,  dry  at  212°  and  then  at 
248",  until  it  ceases  to  lose  weight,  i.  The  loss  gives  the 
water.  2.  Take  the  mass  thus  obtained  and  calcine  in 
a  porcelain  crucible  at  as  low  a  temperature  as  possible; 
the  loss  in  weight  gives  the  organic  matter,  and  the  residue 
the  ash.  It  is  desirable  to  saturate  the  calcined  residue 
with  ammonium  carbonate  before  weighing,  and  then  to 
heat  again  to  an  elevated  temperature.  3.  Dissolve  with 
the  aid  of  gentle  heat  the  ash  obtained  in  2,  in  as  little 


ANALYSIS   OF   SALIVA,  TEETH,   ETC.  559 

moderately  dilute  hydrochloric  acid  as  possible;  add 
ammonia  in  excess  to  the  solution;  a  precipitate  is  thrown 
down,  chiefly  of  calcium  phosphate,  with  a  little  magne- 
sium phosphate  and  calcium  fluoride.  Filter,  and  wash 
the  precipitate  with  water  containing  ammonia.  4.  To 
the  filtrate  add  ammonium  oxalate  to  complete  precipita- 
tion, boil,  filter,  dry  the  precipitated  oxalate  of  calcium, 
ignite,  and  weigh;  the  result  is  the  amount  of  calcium 
carbonate.  5.  Go  back  to  the  precipitate  obtained  in  3, 
dissolve  in  strong  acetic  acid  with  the  aid  of  heat  (calcine 
any  remaining  undissolved,  and  estimate  as  pyrophos- 
phate), and  to  the  solution  add  ammonium  oxalate;  boil 
and  lay  aside  for  12  to  24  hours;  collect  the  precipitated 
calcium  oxalate  on  a  filter,  wash,  dry,  and  ignite  both  pre- 
cipitate and  filter.  Care  must  be  taken  not  to  heat  too 
strongly,  and  it  is  always  advisable  to  moisten  the  precip- 
itate with  ammonium  carbonate  before  drying  at  a  mod- 
erate heat  and  weighing.  The  result  is  calcium  carbonate. 
Calculate  the  total  amount  of  lime  by  adding  the  figures 
obtained  in  4  and  5,  and  making  the  following  proportion: 

100  :  40  =  weight  obtained  :  x 

CaCOa     Ca. 

6.  Evaporate  the  filtrate  of  5  to  small  bulk,  and  also 
the  washings  of  5,  mix  with  excess  of  ammonia,  stir  well, 
boil,  lay  aside  for  12  hours;  collect  on  a  filter,  wash  with 
water  containing  ammonia,  dry,  ignite  to  redness,  weigh. 
Calculate  the  magnesia  by  the  following: 


174 

'yrophosphate 

of 
magnesium. 

80  =  weight  obtained  : 

Magnesia. 

;  X, 

(2  molecules). 

7.  To  the  washings  and  filtrate  obtained  in  6,  add  a 
mixture  of  magnesium  sulphate,  ammonium  chloride,  and 
ammonia,  lay  aside  for  24  hours,  filter,  wash  with  water 


560  DENTAL   CHEMISTRY. 

containing  ammonia,  dry,  ignite  to  redness,  weigh.     Cal- 
culate the  phosphoric  acid  by  the  following: 
I  :  0.216  =  weight  obtained  :  x. 
576.     III.    Qualitative  and  quantitative  analysis  of  tartar: 

A.  I.  Take  a  gram  of  tartar,  calcine  in  air,  dissolve 
residue  in  nitric  acid;  the  part  remaining  undissolved  is 
silica.  2.  Boil  the  nitric  acid  solution  for  two  hours 
with  great  excess  of  pure  sodium  carbonate,  filter,  and  the 
bases,  lime,  magnesia,  etc.,  remain  on  the  filter  as  carbon- 
ate or  oxide.  3.  Wash  the  precipitate  well,  add  ammo- 
nium chloride  in  excess,  then  ammonia.  A  precipitate 
shows  presence  of  iron.  Now  precipitate  the  calcium  by 
adding  excess  of  ammonium  carbonate.  Filter.  4.  To 
the  filtrate  add  sodium  phosphate,  and  a  slight  precipitate 
of  ammonio-magiiesiuiii  phosphate  is  obtained,  which 
after  24  hours  is  complete.  Calcination  gives  very  slight 
residue,  so  that  the  magnesia  may  be  reckoned  as  a  trace. 

B.  I.  Now  take  a  fresh  supply  of  tartar,  reduce  to 
fine  powder,  weigh,  treat  with  boiling  water,  which  re- 
moves soluble  alkaline  salts  and  a  part  of  the  organic 
matter.  F'ilter,  evaporate  filtrate  to  dryness,  calcine,  and 
the  residue  consists  in  the-main  of  chlorides  and  sulphates 
and  should  be  weighed. 

2.  Take  the  precipitate  obtained  in  i,  dry,  weigh,  cal- 
cine in  an  open  porcelain  crucible,  weigh.  Loss  is  animal 
matter. 

3.  Take  residue  obtained  in  2,  boil  in  concentrated  sol- 
ution of  ammonium  chloride,  which  converts  all  the  cal- 
cium carbonate  into  calcium  chloride,  filter,  treat  filtrate 
with  calcium  oxalate,  wash  the  precipitate,  dry,  calcine, 
weigh,  and  the  result  is  the  carbonate  of  calcium. 

4.  Take  precipitate  obtained  in  3,  wash  it  off  from  the 
filtei  paper,  dissolve  in  nitric  acid;  all  is  dissolved  except  a 
slight  residue  (silica):  which  should  be  washed,  calcined, 
and  weighed.     The  result  is  the  amount  of  silica. 


ANALYSIS   OF   SALIVA,   TEETH,   ETC.  561 

5.  Add  to  the  nitric  acid  solution  obtained  in  4,  some 
ammonia — enough  to  overcome  the  acidity.  The  phos- 
phates are  precipitated.  Now  add  acetic  acid  in  excess; 
part  of  the  precipitate  is  dissolved,  part  is  not.  Filter. 
Collect  the  precipitate  on  the  filter,  wash  it  off,  calcine, 
and  weigh.     The  result  is  phosphate  of  iron. 

6.  The  filtrate  contains  the  calcium  phosphate:  neu- 
tralize with  ammonia,  then  add  ammonium  oxalate,  filter, 
collect  precipitate  on  filter,  wash,  calcine,  weigh,  and  the 
result  is  calcium  carbonate.  Calculate  the  lime  from  this. 

7.  To  the  filtrate  obtained  in  6,  add  ammoniacal  mag- 
nesium nitrate,  and  in  24  hours  triple  phosphate  is  com- 
pletely precipitated;  collect  on  filter,  calcine,  weigh,  and 
calculate  the  phosphoric  acid  from  the  weight  as  pyro- 
phosphate. 

ANALYSIS    OF   URINE. 

577.  A.  Note  the  quantity  of  urine  voided  in  24  hours, 
the  color,  odor,  specific  gravity  (using  urinometer,  section 
563),  reaction,  (using  litmus,  section  563,  11),  transparency, 
and  consistence.  Normal  urine  is  excreted  in  quantity 
about  three  pints  in  24  hours,  of  straw-yellow  color,  aro- 
matic, characteristic  odor,  1015  to  1025  in  specific  gravity, 
clear,  with  slight  mucous  "  cloud "  settling  as  the  urine 
stands;  normal  urine  is  an  easily  dropping  fluid  like 
water. 

B.  Get  the  urine  perfectly  clear  by  filtering,  if  neces- 
sary, through  a  number  of  filter-papers  folded  together, 
then  test  for  albumin.  Place  clear,  filtered  urine  to  depth 
of  an  inch  in  a  test-tube;  hold  latter  inclined,  and  allow 
pure,  colorless  nitric  acid  to  flow  down  side  of  test-tube 
into  the  urine.  Use  a  nipple-pipette  for  delivering  the 
acid.  A  clear-cut  whitish  band  of  coagulated  albumin 
will  be  seen  at  the  juncture  of  urine  and  acid,  if  the  urine 
contains  albumin.  Confirm  by  taking  fresh  amount  of 
clear,  filtered  urine  and  pouring  into  test-tube  until  two- 


502  DENTAL   CHEMISTRY. 

thirds  full;  add  a  drop  or  two  of  acetic  acid  and  heat 
upper  part  of  column  of  urine,  holding  test-tube  at  the 
bottom  between  thumb  and  fore-finger.  A  turbidity  seen 
in  the  heated  portion  indicates  albumin. 

C.  Test  for  sugar,  first  removing  albumin,  if  any  is 
present,  by  boiling  the  urine  to  which  a  drop  of  acetic  acid 
has  been  added,  and  filtering.  Test  the  filtered  urine  for 
sugar  as  in  section  569,  A.3.  Or  boil  the  filtered  urine 
with  an  equal  bulk  of  Liquor  Potassas  and  a  decided  yel- 
low coloration  becoming  darker  indicates  sugar.  Pay  no 
attention  to  "  flocks"  seen  in  the  liquid,  as  these  are  merely 
precipitated  phosphates. 

D.  Test  for  bile  precisely  as  for  albumin,  test  i,  using, 
however,  nitrous  acid  instead  of  nitric.  [Nitrous  acid  may 
be  made  by  boiling  nitric  acid  with  a  bit  of  wood  as  end  of 
tooth-pick].  A  set  of  colors  will  be  seen  at  the  juncture, 
if  bile  is  present.  Of  the  colors,  green  is  the  most  con- 
stant and  the  first  in  order  from  above  downward. 

E.  Let  four  fluidounces  of  the  urine  settle  in  a  conical 
glass  vessel  covered  over  to  keep  out  dust.  After  the 
sediment  has  well  settled,  pour  off  supernatant  urine  and 
test  sediment  chemically  or  examine  with  microscope.  [Use 
of  the  latter  is  to  be  preferred,  but  will  not  be  considered 
here].  Test  for  urates  by  warming  a  little  of  the  sediment 
in  a  test-tube.  If  gentle  heat  dissolves  the  sediment,  it 
is  composed  of  urates.  If  not,  add  acetic  acid,  shake  well 
and  warm;  if  now  it  clears,  phosphates  are  in  the  sediment. 
If  no  results  thus  far,  take  fresh  amount  of  the  sediment 
and  add  a  drop  or  two  of  Liquor  Potassee;  if  the  sedi- 
ment become  stringy,  pus  is  present. 

Blood  may  be  recognized  by  the  color  imparted  to  the 
sediment,  which  does  not  clear  on  being  heated.  Uric  acid 
is  often  recognized  by  the  naked  eye,  as  it  occurs  in  the 
form  of  reddish  grains  on  the  side  or  bottom  of  the  glass. 

F.  Estimate  urea  the  chief  normal  constituent  of  urine, 


ANALYSIS   OF   SALIVA,  TEETH,   ETC.  563 

(quantity  20  to  40  grammes  daily).  Use  any  of  the  con- 
venient instruments,  as  Marshall's,  Greene's,  Doremus's, 
Squibb's,  some  of  which  may  be  obtained  with  full  direc- 
tions for  use  from  the  various  dealers.* 

♦For  further  information  on  this  subject,  the  reader  is  referred  to 
the  author's  work  on  "  Diseases  of  the  Kidneys." 


564 


INDEX. 


Absorbents 325 

Acetal: 224,330,337 

Acetamide 227 

Acetanilid 337 

Acetates 65,291 

Aluminium 292 

Plumbic 292 

Reactions 4gi 

Acetic  acid 291 

Acetone 225 

Acetono-resorcin 330 

Aceto-nitrite 231 

Aceto-ortho-toluol 337 

Acetophenone 330.337 

Acetyl  chloride 226 

Acid 

Acetic 225,2  I 

Acrylic 230 

Alpha-naphthoic 237 

Amido-acetic 231 

Amido-caproic 316 

Amido-fatty 227 

Anisic 330.337 

Arsenous 177 

Benzoic 234,235,292 

Beta-napthoic 237 

Boracic...' 176 

Boric 176 

Butyric 225 

Camphoric 335 

Caproic 225 

Carbolic 267 

Carbonic 207 

Chromic 214 

Chrysophanic 237 

Cinnamic 235,334 

Citric 230,300 

•    Dibromgallic 335 

Eugenic 294 

Fatty.. 225 


Formic 225 

Gallic 235,282 

Glycocollic 230 

Hydrochloric 115 

Hydrocyanic 231,294 

Hydrosulphuric 63 

Isovaleric 226 

Lactic 230,295 

Malic 230 

Muriatic 115 

Nitric 188 

Oleic 227,294 

Oxalic 230,295 

Oxybenzoic 298 

Oxynaphthoic 329 

Palmitic 225 

Phenic 267 

Phenylacetic 334 

Phosphoric 181,183 

Picric 233 

Propionic 225,226 

Salicylic 235,298 

Sarco-lactic 296 

Sozolic 299 

Stearic 225 

Succinic 2.'5o 

Sulphanilic 232 

Sulphocarbolic 234 

Sulphovinic 229 

Sulphydric 157 

Sulphuric 158 

Tannic 235,282 

Tartaric 230.300 

Trichloracetic 227,292,335 

Uric 231.316 

Valeric 225,300 

Acid-albumin 537 

Acid  chlorides 226 

Acids 55 

Formulas 56 

Properties 395 

Radicals 218 

Reactions 492 


INDEX. 


565 


Acid  salts 59»99 

Aconitine 302 

Reactions 500 

Acraldehyde 230 

Acrolein 230 

Actinic 19 

Action  on  teeth 

Of  chemicals 346 

Adhesion 5 

Adonidin 312 

Affinity 75 

Agathin 233,337 

Aich's  metal 209 

Alar.tol 272,329 

Albumin 314 

Albuminates 315 

Albumose 539 

Alcohol 260 

Allyl 230 

Aromatic 234 

Benzyl 23! 

Reactions 49 

Alcohols 259 

Diatomic 230 

Monohydric 223 

Phenol 235 

Trihydric... 230 

Aldehyde 259 

Salicyl 23; 

Aldehydes 224,259,289 

Phenol 235 

Alizarine 237 

Alkalamides 62 

Alkali-albumin 507 

Alkaloids 301 

Natural 301 

Reactions 497 

Alkyls 229 

Alloys 89 

Analysis Sn 

Fusible 164 

Preparation 507 

Properties 90 

Quantitative  analysis 511 

Tests 507 


Alpha-naphthol 329 

Alstonine 310 

Alum 195 

Ammonia 19J 

Ferric 195 

Potash 195 

Alumina 196 

Aluminium 191 

Acetate , :  292 

Acetico-tartrate 331 

Alloys 194 

Boroformicate 331 

Experiments  with 432 

1  norganic  compounds 196 

Metallurgy 192 

Reactions  of 471 

Alumnol 331 

Amalgams 1 39 

Alloys 149 

Ames 142 

Antimony 141 

BOGUES 146 

Cadmium 141 

Chandler's 142 

Copper 141 

Discoloration  of 150 

Gold 146 

Hardman's : 149 

Lawrence's 149 

Palladium 146 

Platinum 146 

Properties  of <  •  •  149 

ROLLINS'S 142 

Silver 147 

Tellurium 148 

Tin 148 

TOMES'S 145 

townsend's 149 

Weagant's -. 143 

Zinc 148 

Amides 227 

Amido 232 

Amidocaproic  acid 316 

Amines 62,229,302 

Ammonia 186 

Ammonium 65 

Compounds 102,103 

Reactions 474 


566 


INDEX. 


Amorphous 17 

Amphi-creatinine 239 

Ampere 24 

Ampere's  Law 13 

Amyl 

Nitrite 229,281 

Amylene  hydrate.  .  .  .331,337 

Amyloid  substance 315 

Amyloses 274 

Analgene  238,331 

Analysis 34 

Blowpipe 447 

Gastric  contents 54i 

Groups  of  metals 481 

Qualitative 477 

Separations 481  to  48^ 

Tartar 55^ 

Teeth 55i 

Urine 56 

Volumetric 554 

Anatase 205 

Anglesite 134 

Anhydrides 400 

Organic 226 

Anhydrous  acid 65 

Phosphoric  acid i8i 

Anilids 233 

Aniline 232 

Anise 248 

Anthrarobin 331 

Anthracene 237 

Anticholerin 381 

Antifebrin 310 

Antikamnia 33i»337 

Antikol 337 

Antimony 174 

Alloys 175 

Butter 175 

Compounds 175 

Experiments 441 

Metallurgy 175 

Reactions 463 

Antinervin 331-337 

Antipyrin 231,310 


Antisepsin 233,331,337 

Antiseptics 327 

Dental 326,327 

Volkmann's 334 

Antispasmin 337 

Antithermin 233,332,337 

Antitoxin 240 

Anthrarobin 331 

Apomorphine 310,312 

Apothecaries' weight. .. .   26 

Apparatus 376 

Aqua Ill 

Ammoniae 103 

Chlori 115 

Fortis 188 

Arbutin 311 

Arecoline 311,312 

Argentamine 332 

Aristol 230,234 

Aromatics 232 

Arsenates 60 

Arsenic 177 

Antidote 179 

Experiments  with , 441 

Opaque 178 

Reactions  of 4C<j 

Vitreous 178 

Arsenites 60,178 

Arsenous 

Acid 177 

Anhydride 177 

Reactions 458 

Arsines 230 

Artiads 46 

Artificial  teeth 197 

Asaprol 237,331,337 

Asbestos 132 

Asepsin 233,337 

Aseptol 234 

Asparagin 338 

Aspidospermine 311 

Atmosphere 161 

Atom 2,35,36 

In  molecule 37 


INDEX. 


567 


Atomic 

Theory 2 

Weight 34,41 

Atomicity 40 

Atropine 303 

Reactions 500 

Attraction 3 

Chemical 75 

Auric 

Chloride 173 

Oxide 173 

Avoirdupois  weight 26 

Avogadro's  law 13 

Axes 18 

Axle 8 

Babbitt  metal 137 

Bacillus 240 

Bacteria 320,321 

In  air 162 

Bacteridia 322 

Bacteriens 322 

Baking  soda 99 

Balance 372 

Balsams 255 

Baptisin 312 

Barium 117 

Chloride 117 

Nitrate , 117 

Reactions 472 

Base-plate 

Gold 172 

Bases 55,57 

Properties 395 

Batteries 20,21,22 

Beakers 362 

Beaten  gold 168 

Bebeerine 311 

Beers 262 

Bees-wax 283 

Bell  metal . .  . .- 137 

Bending  rubber 514 

Benzacetin 332 


Benzal 232 

Benzaldehyde 234,235 

Benzanilid 332,337 

Benzene 219 

Series 232 

Benzine 242 

Benzoate 

Ammonium 293 

Benzoic  acid 293 

Benzoinol 338 

Benzonaphthol. . .  332,337.338 

Benzosol 332,336 

Benzoyl  eugenol 332,336 

guaiacol 336 

Benzyl 232 

Bergamot  oil 248 

Betaine 238 

Beta-naphthol 258 

Betol 237,299,329,332,337 

Bicarbonate 

Of  sodium 99 

Bichromate 

Battery 21 

Bichromates 60,214 

Bilineurin 230 

Binaries 48 

Binary  formulas 49 

Biniodide  of  mercury  ....154 
Bismuth 162 

Alloys 164 

Beta-naphtholate 337 

Compounds 163 

Experiments 437 

Metallurgy 163 

Nitrate 163 

Oxyiodide 329 

Reactions 457 

Salicylate 332.337 

Subnitrate 163 

Tribromphenol 337 

Blackening 

Of  amalgams 158 

Blancoline 338 

Blende 125 


568 


INDEX. 


Blood 

Tests 545 

Blowpipe 443 

Blowpipe  analysis 

Antimony 447 

Arsenic 447 

Bismuth 44^ 

Copper 447 

Lead 447 

Silver 447 

Tin 44^ 

Zinc 4^ 

Blowpipe 

Materials 445 

Self-acting 44^ 

Boas's  test 544 

Body I 

Boiling 14,373 

Boldine 311 

Bonds 218 

Bone 339 

Marrow 340 

Boracic  acid 61,176 

Borates 60,63 

Reactions 490 

Borax 101,198,490 

Boric  acid 1 76 

Borine 338 

Boro-glycende 264 

Boro-lyptol 336 

Boron 1 76 

Brass 137 

Brimstone  ....  - 156 

Brittleness 6 

Bromamide 332,337 

Bromides 63 

Reactions 487 

Bromine 113 

Experiments 427 

Bromol 332.337 

Brookite 205 

Bronzes 137.138 


Brucine 309 

Reactions 499 

Buccal  mucus 354 

Bunsen  burners 363 

Burettes 362 

Burnett's  fluid 127 

Burns 97 

Butter 228 

Of  antimony : i75 

Butterine 228 

Butyl  chloral 224 

iJocoa  butter 183 

Cacodyl 230 

Cadaverine 230,238 

Cadmium 132 

Amalgam 141 

Sulphate 133 

Caffeine 310,312 

Reactions 499 

Cajuput  oil 248 

Calcium 117 

Carbonate 119 

Compounds 118 

Experiments 431 

Fluoride 121 

Glyceroborate 265 

Hydrate 120 

Hypophosphite 123 

Lactophosphate 298 

Oxide 120 

Phosphate 122 

Reactions '472 

Sulphate 118 

Sulphite 122 

Calculi,  salivary 358 

Calomel 152 

Calx  chlorata 122 

Camphene 245 

Camphor 254 

Monobromated 214 

Cancer  of  stomach 544 

Cane  sugar 273 

Cannabine 305 

Cannabis 305 


INDEX. 


569 


Cannabinum  tannicum . . .  305 

Capillarity 9 

Carat 

Determination 5o5 

Caraway  Oil 249 

Carbohydrates 230,273 

Carbo  ligni 205 

Carbon 205 

Compounds 207,216 

Dioxide 414 

Disulphide 207 

Experiments 413 

Monoxide 413 

Oxides 207 

Tetra-chloride 229 

Carbonates 60 

Reactions 486 

Carbon  disulphide 

Experiments 421 

Carbonic  acid 207 

Experiments 415 

Caries 347 

Microbe 323 

Of  bone 341 

Theories 348 

Carmine 239 

Carvacrol 234 

Iodide 333 

Casein 537 

Cassius,  purple  of 174 

Catalytic  action 76 

Cell 20 

Cellulin 276 

Celluloid 277 

Cellulose 276 

Cement 121,339 

Cements 1 30 

Tests 572 

Centigrade 33 

Cerium 191,198 

Oxalate 26s 

Chains 218 

Closed 219 


Charcoal 205,206 

Chemical  action 68 

Chemical  arithmetic 73 

Attraction 75 

Change 66,387,388 

Combination 390 

Effects  of  light ig 

Philosophy 34 

Chemical  solution 15 

Chemically  pure  gold 166 

Chemism 35 

Chemistry 34 

Experiments 360 

Organic 216 

Chinol 337 

Chinoline 304 

Chloral 224 

Chloralamide 33i»337 

Chloranil 234 

Chloral-ammonium 337 

Caffeine 357 

Hydrate 289 

Menthol 333 

Chloralose 333 

Chlorates 60,63 

Reactions 488,48 

Chlorides 63 

Reactions 487 

Chlorhydric  acid 115 

Chlorinated  lime 122 

Chlorine 112 

Compounds 115 

Experiments .424 

Water 115 

Chloro-benzene 232 

Chloroform 229,284 

Reactions 465 

Chlorophenol 333.334 

Chloryl 333 

Cholin 238 

Chondrin 315 

Chromates 60,63 

Chromic  acid 214 


570 


INDEX. 


Oxide ai5 

Chromium! 214 

Compounds 214 

Experiments 435 

Reactions 47o 

Chrysarobin 237 

Cinnabar I39'I53 

Cinnamon  oil 249 

Circuit 20,23 

Citric  acid 230 

Classification 

Elements 76,93 

Organic  compounds 222 

Classifications 93 

Coagulated  albumin 315 

Proteids 538 

Coal 206 

Cobalt 213 

Reactions 472 

Cocaine 230,305 

Reactions 5oi 

Salts 306 

Codeine 

Reactions 49g 

Cohesion 5 

Colchicine 312 

Collagens 315 

Collodion 276 

Colloids 17 

Color 

For  teeth 205 

Of  teeth 213,21 5 

Of  rubber 514 

Combustion 221 

Compound 35.36 

Binary 48 

Molecules 46 

Ternary 24 

Compound 

Ethers 277,281 

Compressibility 5 

Conducting  power 85,86 

Condy's  fluid 98 

Coniine 238,  31 1 

Reactions 498 


Constants  of  the  elements  39 

Convallamarin 311 

Convallarin 311 

Copper 135 

Alloys 137 

Compounds 138 

Experiments 43fr 

Metallurgrv 136 

Reactions 45^ 

Cork-borer 365 

Coronillin 312 

Corrosive  sublimate 150 

Corrugated  gold 169 

Cotarnine 338 

Counterpoise 373 

Coulomb 23 

Cream  of  tartar 300 

Creasotal 333-334 

Creasote 265 

Carbonate 334 

Creatine 231 

Creatinine 231 

Creolin 3295331 

Creasol 234 

Cresapol 334 

Cresalol.. 333.334,337 

Cresoliodide 335 

Cresols 234 

Cresylic  acid n  . .  329 

Greta  praeparata 117 

Crocoisite 134 

Croton  chloral 290 

Croton  oil 284 

Crown  enamels 197 

Cruso-creatinine 239 

Cryolite 117 

Crystal  gold 167 

Crystalline  structure.  .  .82,86 

Crystalloids 17 

Crystallization 17 

Crystals 17 

Cupric  sulphate 138 


INDEX. 


571 


Current 

Electric 20 

Induced 22 

Cyanides 64,231 

Reaction 487 

Cyanogen  compounds. .  .230 

Cytisine 310 

Decay 221 

Decomposition 

71,221,391,394 

Definite  proportions 47 

Deliquescence 16 

Density 13,47 

Dental 

Amalgams I39.i49 

Antiseptics 323 

Deodorizers 288,328,32*^ 

Rubber 2^^ 

Dentine 339 

Analysis 342 

Deodorizers 328 

Derivatives 220 

Derived  albumins 315 

Dermatol 235,333 

Destructive  agents 325 

"  distillation..    15 

Dextrin 275 

Dialysis 17 

Dialyzed  iron 212 

Dialyzer 17 

Diaphtherin 238,333 

Diaphthol 335 

Diastase 318 

Diatomic 40 

Diazo 233 

Dichromates 60 

Digestion 

Gastric 539 

Pancreatic 540 

Digitalin 312 

Digitoxin 312 

Di-iodoform 336 


Di-isobutylorthocresol 

Iodide 336 

Diluents 325 

Dimethylamine 230 

Dimetric 18 

Diphenylamine 233 

Dishes 366 

Discoloration  of  fillings . .  1 50 

Disinfectants 326 

Disinfection 325 

Displacement 9 

Distillation 15,386 

Ditaine 310 

Diuretin 31 1.338 

Divisibility 4 

Double  decomposition ...  69 

Double  salts 59 

Dry  distillation 221 

Ductility 61,85 

Dutch  gold 172 

Dyads 113. 117 

Negative ii7 

Positive 117 

Dynamo 23 

Eau  de  Javelle 102 

Ebonite 251 

Ecgonine . , 238 

Effect  of  metals  on  gold.  171 

Efflorescence 16 

Elasticity 5 

Elasticin 343 

Elastin 315,316 

Electricity 20,23,74 

Dynamic 23 

Galvanic 23 

In  the  mouth 23 

Magneto 24 

Quantity 24 

Static 24 

Thermo 24 

Electro 

Negative 42 

Positive 42 


572 


INDEX. 


Electrodes 20 

Electrolysis 23 

Electro-motive  force....   24 

Element 35»36 

Elements 39 

Classifications 76,80,93 

Negative 39,42 

Positive 39,42 

Table  of 39 

Empirical  formulae 217 

Emulsions 531 

Enamel 339 

Analysis 342 

Enamels 197 

Energy 7 

Enzymes 317 

Equations 71 

Equivalence 43 

Erythrophleine 310 

Hydrochlorate 337 

Eserine 310 

Essential  oils 246 

Esters 224,228 

Ether 278 

Reactions 49^ 

Sulphuric 278 

Ether  fortior 279 

Ethereal  salts 228 

Ethers 223,259,277 

Ethyl 

Aceto-acetate 229 

Bromide 228.28° 

Chloride 22*^ 

Nitrate 229 

Nitrite 229:281 

Series 258 

Ethylene 229 

Periodide , 336 

Ethyl-oxy-caffeine  ..... .310 

Eucalyptol 272 

Eucalyptus 328 

Eudoxin 338 

Eugenic  acid 234 

Eugenol 234 


Eugenol-acetamide 337 

Euonymin 312 

Euphorin 334.337 

Europhen 334.336 

Eurybin 312 

Evaporation 15 

Exalgin 233,237 

Expansibility 5,82 

Explosives 378 

Eyes 378 

Danger  to 378 

Factors 66,71 

Fahrenheit 33 

Farad 23 

Faradic  current 22 

Fats 227,277,283 

Crystallization  of 531 

Experiments 527 

Fatty  acids 225,530 

Fehling's  Solution 523 

Feldspar 197 

Ferment 

Butyric 320 

Thrush 320 

Fermentation 221,316 

Microbe  of 322,323 

Putrefactive 320 

Sugars 526 

Ferments 317,321 

Acetic 319 

Butyric 319 

Lactic 296,319 

Organized .'...317,318 

Soluble 317 

Unorganized 317 

Yeast 319 

Ferric 

Compounds 211,212 

Hydrate 179 

Valence 52 

Ferricyanides 60,64 

Ferrous 

Compounds 212 

Valence 25 


INDEX. 


573 


Ferrocyanides 60,64 

Fibrin 315.538 

Filters 361 

Fixed  oils 244,284,527 

Flame 443 

Oxidizing 444 

Reducing 444 

Flowers  of  sulphur 156 

Fluid 7 

Extracts 262 

Fluorides 63,340 

Fluorine 39.44. 1 16 

Fluor-spar 1 1 7, 1 2 1 

Fool's  gold 172 

Foot-pound 7 

Force 7 

Formalin 334,336 

Formamide 227 

Formanilid 337 

Formulas 47 

Empirical 217 

Graphic 217 

Hydrates 58 

Molecular 217 

Rational 217 

Salts 59 

Structural 217 

Ternary 54,63 

Fractional  distillation...    15 

Friction 9 

Frits 198 

Fulcrum 8 

Fungi 321 

Funnels 36 1 

Furfurane 231 

Fusel  oil 263 

Fusibility 

Of  alloys 90 

Of  metals 84 

Fusion 

Alloys 367 

Laws  of 14 

Gadinine 235 

Galena 134 


Gallaceto-phenone 235 

Gallic  acid 282 

Gallobromol 335 

Galvanic  electricity. .  ..20,  25 

Galvanized  iron 1 26 

Gas 7 

Illuminating 206 

"Water" .  ^ 106 

Gases 7 

Experiments  with 404 

Gasoline 242 

Gastric  juice 541 

Guy  Lussac's  law 67 

Gelatin 31 5 

German  silver 106 

Germicides 325 

Gerontine 239 

Glacial  phosphoric  acid..  183 
Glass 

Rods 362 

Tubes 362 

Globulin 314,536 

Glucose 274 

Glucosides 282,3 1 1 

Glycerin 263 

Glycerins 230 

Glycerites 264 

Glyceroborates 265 

Glycerol 230,  263 

Experiments 529 

Reactions 496 

Glyceryl 263,277 

Glycine 231 

Glycocoll 227 

GlycocoUic  acid 230 

Glycogen 527 

Glycols 230 

Glycothymoline 338 

Glyoxal 230 

Goa  powder 237 

Gold 164 

Alloys 170  to  172 


574 


INDEX. 


Amalgams 146 

Base  plate 172 

Cohesive 169 

Compounds 173 

Corrugated 169 

Crystal 167 

Dutch 172 

Experiments  with 442 

Fine 169 

Fool's 172 

Green 170 

Metallurgy  of 165 

Mosaic 172 

Plato 173 

Pure 166 

Precipitated 165 

Quartz 165 

Reactions  of 466 

Red 172 

Refined 166 

Solders 173 

Talmi 172 

Yellow 170 

Graduates 1 73 

Grape-sugar 274 

Gravity  battery 21 

Guaiacol 234,336 

Salts  of 336 

Guaiacum 255 

Guanidine 231 

Guanin 231,239,316 

Gum 275 

Enamel 198 

Resins 255 

Tragacanth 275 

Gums .256 

Gutta  percha 252,254 

Gypsum 118 

Haines's  solution 523 

Halogen 

Inorganic  compounds  110,111,112,113 
Ethers 228,277 

Hardness 

Of  bodies 6 

Of  waters 118,120 

Hartshorn 103 

Heat 14.74 


Heliotropin 336 

Hematite  209 

Heteroxanthine 239 

Hexads 44,208 

Hexagonal 19 

Hill's  stopping 249,253 

Homatropin, 312 

Homologous  series.  .219,258 

Honey 275 

Horse-power 7 

Hydracetine 233,335,337 

Hydracids 55 

Hydrargyrum 138 

Hydrated  acid 66 

Hydric 

Acetate 291 

Chloride 113,115,426 

Dioxide 111,402 

Nitrate 188 

Oxide 108 

Oxalate 230 

Phosphate 182 

Sulphate , 158 

Sulphide 1 57,419 

Tartrate 300 

Hydrides 94 

Hydriodic  acid 63,487 

Hydrocarbons 222 

Hy  drobromic  acid 63 

Acelytene 223 

defines 223 

Hydrates 57 

Hydrazines 233 

Hydrazones 233 

Hydrocollidine 238 

Hydrocyanic  acid 64,294 

Hydroferricyanic  acid...  64 
Hydroferrocyanic  acid. , ,  64 
Hydrofluoric  acid 63 

Experiments 428 

Hydrogen 107 

Acetate 291 

Chloride 113,115,426 

Dioxide 111,402 


INDEX. 


575 


Nitrate i88 

Orthoboiate 176 

Oxide 108 

Oxalate 230 

Peroxide iii 

Phosphate 182 

Sulphate 158 

Sulphide ". IS7»4I9 

Hydrogen 

Experiments  with 404 

Hydrometers 12 

Hydronaphthol 336,337 

Hydroquinone. .  .234,335,337 

Hydrosulphuric  acid 63 

Hydroxides 37 

Hygroscopic 16 

Hyoscine 337 

Hyoscyamine 310 

Hypnal 224,337 

Hypnoacetin 338 

Hypnone 235,337 

Hypnotics 337. 

Hypochlorites 60,64 

Hypophosphites 60,64 

Hypothesis 2 

Hypoxanthine 231,239 

Illuminating  gas 206 

Imides 229 

Impenetrability 4 

Inclined  plane 9 

India  rubber 251 

Indigo 236 

Carmine 236 

Indoe 236 

Indoxyl 236 

Induction 22 

Inorganic 

Chemistry 94 

Formulas 48,52,56,60 

Inosite 234 

Insoluble  substances. 382,384 
Iodides 63 

Reactions  of 487 

Iodine 112 


Experiments 427 

Preparations 113 

Iodine  tri-chloride 329 

lodo-casein 336 

lodo-eugenol 336 

Iodoform ; . . . .  229,287 

lodoformin 336 

lodol 288 

lodo-phenacetine 336 

Iridium 204 

Iron 209 

Cast 210 

Pig 210 

Wrought 210 

Iron 

Compounds 211 

Experiments 433 

Metallurgy 209 

Reactions 468 

Isatin 23 1 

Isatropyl  cocaine 311 

Isologous 220 

Isomeric 221 

Isomerism 220 

Isometric 18 

Isomorphous 18 

Jerubebine 311 

Kaolin 197 

Kairine 238 

Keratin 343 

Kerosene 242 

Ketones 225,290 

Aromatic 235 

Kresin 336 

Labarraque's  solution. . .  .  102 

Lac 256 

Lactates 298 

Lactic  acid 230 

Lactol 335.337 

Lacto-phenin 335-337 

Lacto-phosphates 298 

Lactucin 312 

Lamine 311 


576 


INDEX. 


Lantanine 312 

Lardacein 315 

Laughing  gas 186 

Experiments 410 

Law 2 

Avogadro 13,37 

Berthollet 69 

Charles. 13 

Definite  proportions 47.67 

Gay  Lussac 67 

Lavoisier 67 

Mariotto 13 

MultiDle  proportions 47 

Law  of  fusion 14 

"      "    solubilities 70 

Lead 133 

Compounds 135 

Dental  uses 134 

Experiments 436 

Metallurgy 134 

Plaster 228 

Reactions 452 

Leaf-gold 163 

Leptandrin 312 

Leptothrix 322,323 

Leucin 227,316 

Leucomaines 239 

Lever 8 

Light 74 

Lime 66, 1 20 

Fluoride 121 

Water 12I 

Limonite 209 

Linking  function 55 

Liquid 7 

Liquid  diffusion 16 

Liquor in 

Potassae 97 

Listol 336 

Litharge 135 

Lithium 103 

Litmus 234,367 

Lobelin 312 

Loretin 335 


Losophan 335 

Lunar  caustic 106 

Lustre 83 

Lycetol 338 

Lysidin 338 

Lysol 336,335 

Machine 7 

Magnesia  . . . . , 66 

Alba 123 

Magnesium 123 

Compounds .123 

Experiments 430 

Reactions 473 

Magnetite 209 

Magneto-electricity 24 

Magnitude 4 

Malachite  greens 236 

Malakin 336 

Malleability 6,8:; 

Malleable  iron 210 

Manganese 205 

Compounds 208 

Experiments 434 

Reactions 469 

Manipulations,  chemical.  373 

Mannheim  gold 172 

Margarine 228 

Marsh-gases 258 

Mariotte's  Law 13 

Mass 3 

Matter 1,4 

Measures 26 

Melting  points 39 

Mendeleef's   law 78 

Menthol 272 

Mercaptans 229 

Mercuric  albuminate  . . .  .329 

Oleate 295 

Oxycyanide 329 

Mercury 138 

Compounds 150  to  155 

Dental  uses 139 

Experiments 439 


INDEX. 


577 


Metallurgy 139 

Reactions 453 

Valence 51 

Mercury  in  saliva 555 

Meta-acids 61 

Meta-elements 40 

Metals 82,84 

Properties 82,83,84 

Tests  for 

Blowpipe 446 

Chemical 451 

Metalbumin 315 

Metalloids 95 

Metameric 221 

Meta-phosphoric  acid. .  .  183 

Methacetin 337 

Methane 258 

Methylal 224,337 

Methylamine 238 

Methylaniline 233 

Methylbutyrate 229 

Methylene 229 

Metre 27 

Metric  equivalents 28 

System 27 

Metric  system 27 

Metric  weights 372 

Meyer,  Lothar 

Classification  of  elements 80 

Microbes 321,323 

Pathogenic 324 

Protection  against 325 

Micrococcus 

Of  saliva 323 

Septicus 324 

Microfarad 23 

Miller 

Experiments  of 327 

Millon's  reagent 534 

Milk  of  lime 121 . 

Milk  sugar 274 

Mineral  oil 244 

Mint  oil 250 


Mixture 36 

Mobility 5 

Molecular 

Mixtures go' 

Motion 4 

Weights 47 

Molecules 3,35,36,40,41 

Monad  (microbe) 322 

Monads 43,94 

Monatomic 40 

Monoclinic 19 

Monsel's  solution 212 

Morphine 307 

Reactions 448 

Salts 307 

Mortar 121,363 

Mosaic  gold 172 

Motion 

Atomic 4 

Molecular 4 

Mouth  washes..  .327,328,338 

Miller's 328 

Muawin 311 

Mucin 315,551 

Mucus 354 

Muriate  of  ammonia 103 

Muriates 66 

Muriatic  acid 115 

Muscarine 238 

Mycoderma 322 

Mydine 238 

Myosin 536' 

Myrrh 255 

Myrtol 273,332 

Mytilotoxine 238 

Napelline 303 

Naphtha 242 

Naphthalenes 236,257 

Naphthols 237,258 

Narceine 310,311 

Nascent  state 75,394 

Native  albumins 314 


578 


INDEX. 


Natural  waters 385 

Necrosis 

Of  bone 34i 

Negative  elements 39 

Radicals 60 

Neroli  oil , 250 

Neurine 229,238 

Neurodin 337 

Nickel 212 

Reactions 472 

IMicotine 238,311 

Reactions 497 

TSIitrates 60,63 

Reactions '. 48S 

Nitric  acid i88 

Experiments 412 

Nitriles 231 

Nitrites 60 

Nitro 232 

Nitro-benzene 232 

Nitrogen 186 

Compounds 186,409 

Experiments 407.411 

Monoxide 186 

Protoxide 186 

Nitroglycerine 230 

Noble  metals 83 

Nomenclature 65 

Notation 40 

Nurnberg  gold 1 70 

Nux  Vomica 309 

Ohm 24 

Ohm's  law 25 

Oils 

Fixed 283 

Volatile 248 

Anise 248 

Bergamot 248 

Cajuput 248 

Caraway 249 

Carvacrol 249 

Ciniiamon 249 

Cloves 249 

Eucalyptus 250 


Eugenol 250 

Gaultheria 250 

Lavender 250 

Mint 250 

Neroli 250 

Pyrethrum 250 

Rose 250 

Sanitas 245 

Turpentine 244 

Oil  of  vitriol 158 

Oleate  of  aconitine 302 

Oleates 295 

Oleic  acid 294 

Olein 283,527 

Oleo-creasote 336 

Oleo-guaiacol 336 

Oleo-margarine 228 

Opening  bottles 375 

Oral  secretions 555 

Orcin 234 

Oreide 172 

Orexine 238 

Organic 

Acids 290 

Analysis 217 

Chemistry 216 

Compounds 216 

Substances 222 

Organized  ferments 317 

Orris 328 

Ortho-acids 61 

Ortho-phosphoric  acid.  ..182 

Osazones 233 

Osmosis 17 

Ossein 315 

Ouabain 313 

Ox-acids 55 

Oxalates 65,295,491 

Oxalic  acid 230 

Oxidation 160,398 

.Oxides 63,400 

Oxidizing 160 

Oxybenzoic  acjd 298 

Oxychloride  ce  ments 1 30 


INDEX. 


579 


Oxygen i6o 

Blowpipes .161 

Experiments 397 

Oxyhydrogen  flame io8 

Oxyhydroquinone 234 

Oxynaphthoic  acid 329 

Oxyphosphate  cements. .  129 
Oxy-propylene-di-iso- 

amyl-amine 311 

Ozone •403 

Pale   gold 1 70 

Palm  oil  soap 228 

Palladium 201 

AmalKam 146 

Papain 313 

Papaverine 311 

Paracresol  salcylate 334 

Paralbumin 315 

Paraldehyde 224,289 

Paraffins 240 

Paraxanthine 239 

Parotid  saliva 353 

Parting  plaster 515 

Parvoline 238 

Pear  oil 229 

Pelletierin 312 

Pental 337 

Pepsin 317,318 

Peptone 315. 537.539 

Percentage  solutions 29 

Periods ']'] 

Perissads 46 

Petroleum 24 1 

Pewter 200 

Phenacetin 234,337 

Phenates 270 

PhenocoU 234 

Phenol 233,267 

Camphor 270 

Reactions 495 

Sodique 270 

Terchloride 270 

Phenols 233 


Phenosalyl 336 

Phenomena 2 

Phenyl 232 

Alcohol 267 

Phenyl-acetylene 232 

Phloroglucine 234 

Phosphates 60,63, 182 

Reactions 490 

Phosphines 230 

Phosphor-bronze 138 

Phosphoric  acids 

181,182,183,185 

Experiments 422 

Reactions 490 

Phosphor-iridium 170 

Phosphorus 180 

Experiments 422 

Physical  solution 15 

Physics I 

Physiological  chemistry. 517 

Physostigmine 500 

Phthaleins 236 

Picnometer 12 

Picrol 335 

Pilocarpine 312 

Pinacones 230 

Pinchbeck 1 72 

Piperazine 230,338 

Piperidine 238 

Piperine 311,312 

Piperonal 336 

Pipette 362 

Plaster 

Work  in 515 

Of  Paris 118 

Platinum 20 1 

Amalgam 147 

Color 202 

Metals 203 

Metallurgy 203 

Reactions 467 

Ware 366 

Plumbic 104 


580 


INDEX. 


Polarization 22 

Poles 20 

Polymorphous 17 

Porosity 5 

Positive  elements 39 

Potassa 66 

Potassium t 95 

Compounds 95.96,97,98 

Experiments  with 429 

Reactions 475 

Sodium 332 

Potato  spirit 263 

Potential 24 

Pouring 374 

Practical  chemistry 397 

Precipitate 70 

Precipitation 387 

Prefixes  di-,  pent-,'^and  tri-  66 

Proto  and  per 65 

sesqui 66 

Pressure 76 

Products 67,71 

Proof  spirit 262 

Properties 

Metals 87,88,89 

Solders 92 

Propione 225 

Propenyl 263 

Proteids 313 

Characteristics  of 535 

Digestion  of 538 

Experiments  with 532 

Tests  for 533 

Pseudoxanthine 239 

Ptomaines 238,301 

Ptyalin 317,318 

Pulley 8 

Pulp  cavity 339 

Purple  of  Cassius 174 

Pus 324 

Putrefaction  .221,314,317,323 

Putrescin 230,238 

Pyrethrum  oil 250 


Pyoctaniu 337 

Pyocyanine 238 

Pyorrhoea 327,335-335 

Pyridine 237 

Pyrocatechin 234 

Pyrogallol 234 

Pyrolusite 208 

Pyromasphite 134 

Pyrophosphate 60 

Pyoroxylin 277 

Pyrozone 332 

Pyrrol 231 

Quantity 

Electrical 24 

Quantivalence 43 

Quicklime 120 

Quicksilver 138 

Quinalgen 337 

Quinine 308 

Reactions 499 

Salts 309 

Sulphate 309 

Quinoline 234 

Quinones 238 

Radiant 7 

Radicals 54,217 

Acid 218 

Negative 60,218 

Positive 218 

Ratsbane 177 

Reactions 68 

Of  acid  radicals 486 

**  acids 486 

"  alkaloids 497 

"  metals 451 

"  organic  substances 495 

"  proteids 533 

"  starch 518 

"  sugars 524 

Xantho-proteic 534 

Reading  formulas 53 

Reagents 68 

Alkaloidal 501 

Bottles 368 

For  gastric  juice 542 


INDEX 


581 


Fehling's 523 

Haines's 523 

Millon's 534 

Uffelmann's 543 

Red-gold 172 

Reduction 401 

Rees's  alloy 200 

Refined  gold 166 

Refining  gold 502 

Regulus  of  antimony. . . .  175 
Relation  of  volumes  to 

weight 31 

Resins 255 

Resistance 

Electrical 24 

Resistance  to  air 86 

Resol 334 

Resorcin 234,271 

Rheophores 20 

Rhigolene 241 

Ring-stands 363 

Robinson's  remedy.  .  .97,269 

Rochelle  salt 300 

Rosanilines 236 

Rose  oil .250 

Rubbers 251 

Tests 515 

Work  in 51S 

Rutile 205 

Safrol 273,328 

Salacetol... 334,335 

Salamandarine 239 

Sal  ammoniac 103 

Salicylates 67 

Salicylic   acid 65,298 

Saliva 349 

Action  of  drugs  in ...  356 

Analysis  ot 547 

Analysis  350 

Changes  in 355.356 

Chordal 354 

Diseases  of 357 

Functions  of 352 

Odor  of 357 


J'arotid 353 

Quantitative  analysis  of 552 

Sublingual 353 

Submaxillary 353 

Salivary  calculi 358 

Salipyrine 337 

Salocoll 337 

Salol 235,299,332 

Salophen 235 

Sal  prunella .97 

Sal  soda 100 

Sal  volatile 103 

Saltpetre 97 

Salt 58,59 

Common loo 

Epsom 123 

Salufer 335 

Sandarach 256 

Sand-bath 363 

Sanitas  oil 245 

Sapocresol 334 

Saponification 263,528 

Sarcinae 323 

Sarkin.. . .' 316 

Saturated  solution. ...  16,217 

Scales 37i»372 

Scillipicrin 338 

Scoparine 313,338 

Scopolamine 313 

Screw 9 

Sectile 84 

Separation 

Metals  from  gold 503 

Series 

Homologous 219 

Sesqui 66 

Shellac 257 

Siderite 209 

Silex 197,205 

Silica ••••....  204 

Silicates 60,121,205 

Silicon 204 


582 


INDEX. 


Silver 1 03 

Alloys 106 

Amalgams i47 

Compounds io7 

Dental  uses 105 

Experiments  with 437 

Metallurgy 104 

Reactions  of 45^ 

Solders 106 

Similor 172 

Skatol 236 

Skeleton '. .  .219 

Slaked-lime 120 

Soap 263 

Soaps 227 

Soda 66 

Sodium 98 

Chloroborate 335 

Inorganic  compounds  ..99,100,101,102 

Experiments 429 

Fluosilicate 335 

Organic  compounds: 

Dithiosalicylate 335 

Ethylate 335 

Formate 335 

Glyceroborate .' 265 

Paracresotate 337.338 

Phenate 270 

Sulpho-salicylate 338 

Reactions 474 

Silico-fluoride .530 

Sulphite,  benzoated 330 

Tetraborate 338 

Solanine 317 

Solders 92,200 

Solid 7 

Soluble  ferments 317 

Solubility 16 

Solution 15,380,381.390 

Solphinol 334 

Solvents 16 

Sophorin 312 

Sozolic  acid 299 

Sparteine 311 ,498 

Spasmotoxine 238,313 

Special  albumins 315 


Specific 

Gravity lo 

Heat 14,83 

**    of  elements 39 

Volume 30 

Speculum  metal, 1 38 

Spermine 239 

Spiegel-eisen 210 

Spirilla 322 

Spirit  of  camphor 366 

Mindererus 291 

Wine 262 

Spirits 262 

Spirochcetae 323 

Sputum 557 

Starch 274 

Action  on 522 

Experiments  with 517 

Stannate  of  gold 174 

Stannic  salts 20 1 ,466 

Stannous  salts 200,465 

States  of  matter 7 

Stearin 283 

Steel 210 

Storage  batteries 21 

Sterilizers 328 

Strontium  reactions 473 

Stibines 230 

Stibium 174 

Stibnite 175 

Stibyl 300 

Strophanthin ....313 

Structure,  metallic 86 

Strychnine ; 309 

Reactions 499 

Styptic 

Collodion 276 

Colloid 282 

Stypticine". 338 

Styracol 334 

Styrene 232 

Subacetate  of  lead 292 

Sublimation 15.383 


INDEX. 


583 


Sublingual  saliva 353 

Submaxillary  saliva 354 

Subnitrate  of  bismuth.. . .  163 

Substances i 

Substitution 220 

Sugars 273 

Cane 273 

Grape 274 

Milk 274 

Tests  for 523 

Sulphaminol 334 

Sulphates 60,63,  ^  5^ 

Reactions, 48g 

Sulphides 63,157 

Reactions 486 

Sulphites  . .  . , 60,63, 1 56 

Reactions 489 

Sulphydric  acid 157 

Sulpho-acids. 55 

Sulphocyanide 

In  Saliva 5So 

Sulphocyanates 64 

Sulphonal 229 

Sulphonic 232 

Sulphovinic  acid 229 

Sulphur 156 

Experiments 416 

Sulphur  lotum 1 56 

Sulphurets 66 

Sulphuretted  hydrogen 

.....157,320,419 

Sulphuric  acid 158 

Experiments 4i7 

Reactions 489 

Sulphuric  ether 278 

Sulphurous  acid '.  1 56 

Experiments 416 

Reactions 489 

Supports 363 

Suppuration 324 

Symbols 37 

Symphorol 338 


Synopsis 

Organic  Chemistry 222 

Synthesis 35 

Syntonin 311 

Systems  of  crystals 18 

Tannin 282 

Tartar 357 

"  Emetic 309 

Tartaric  acid 230 

Tartarlithin 33S 

Tartrates 300 

Reactions 492 

Teeth.... 339 

Affected  by  agents 346 

Analysis 341 

Analyses 344.345 

Artificial 197 

Tellurium 155 

Temperature 14 

Tenacity 6,85 

Tensile  strength 84 

Terebene 245 

Terminations 

— ate 59 

hypo-ite , 59 

hypo-ous 49 

— ic 49 

— ide 48 

— ite 59 

— ous 49 

Tests 

Benzo-purpurin ';43 

Bettendorf's 46s 

Fleitmann's 463 

Marsh 461 

Methyl-violet 542 

Phloroglucin 542: 

Reinsch 461 

Tropaolin 542 

Vanillin 542 

Test-tubes 360 

Tetrads 44,191 

Positive 191 

Negative 19^ 


584 


INDEX. 


Tetra-iodo-ethylene 336 

Thalline , 328 

The  air 

Experiments 408 

Thein .312 

Theobromine 312 

Theory 2 

Thermal  unit 14  t. 

Thermin 237  Toxmes     238 

Thermodin 3^7  Traumatol 338 

Thermometry 23  I"^^,^^"^ 227 


Oxalic  acid 295 

Phosphorus igj 

Potash 07 

Silver  nitrate 107 

Strychnine 30^ 

Sulphuric  acid 159 

Tin :...: 202 

Zinc  chloride 128 

Zinc  compounds 132 


Triads 47 

Positive 162 

Negative 162 

T^i        ,  --     Triangle 36"; 

Thrush 319  Tributyrin 228 


Thioform 336 

Thiophene 231 

Thio-resorcin 336 


Thymacetm 337  Tribrom-phenol 330 

J^y"^°  273  Trichloracetic  acid 22 

J^y"^ols 234  Triclinic m 

-^ in 198  Tricresol "7^6 

^"°y^-;, ^°°  Tricresolamine '.336 

Compounds 200    --r   •        ii      1         •  •^•^ 

Metallurgy 199  J  rimethylamme 238 

Reactions 465  Trimetric ig 

Tinctures.  .    262  Triolein 227 

Titanium 205  Trional 229 

Tolypyrin •  •  •  337  Tripalmitin 227 

Torula '  Triphenylmethane 236 

Toxalbumins 239  Tripsin 317 


Tristearin, 


227 


Tritenyl 263 

Trommer's  test 525 

Tropa-cocaine 311 

Tropine 238 


Toxicology 

Amyl  nitrite 281 

Arsenic 179 

Atropine 383 

Chloral 290 

Chlorine ii^ 

Chloroform 286  Troy  Weight 

Chromic  acid 215  Turmeric 367 

Corrosive  sublimate 152    Turpentine 244 

Croton  oil 284    t-  ^^ 

Ether 280    JyPp 220 

Ethyl  bromide 281   Typhotoxine 238 

Hydrochloric  acid 116    Tyrosiu 23C,3l6 

1^'°!: "3  Tyrotoxicon ". .'238 

Morphine -JoS    <-t^  "J'-' 

Nitre 98  Terpenes 245 

Nitric  acid 190  Terpin 245 


INDEX. 


Terra  alba 1 1 8 

Terraline 338 

Ternaries 54 

Valence 43 

Of  aluminium 52 

"  copper 51,52 

"  iron 52 

"  mercury 51.52 

"  radicals 54 

Variations  in 45 

Valerianates 226 

Valeric  acid 300 

Vanillin 235 

Vapors 7 

Variations  in  valence 45 

Vaseline 243 

Vasogen 338 

Vaughan's 

Table  of  leucomaines 239 

Veratrine 310 

Reactions 500 

Vermillion 153 

Vibriones 322 

Vienna  paste 97 

Vinyl 230 

Vital   force 75 

Volatile 

Compounds 70 

Metals 83 

Oils 247 

Volt 24 

Volume,  specific 30 

Volumetric  analysis 554 

Vulcanizing 1 56 

Vulcanite 251 

Manipulation  of 514 

Ulexin 311 

Uralium 337 

Uranium 135 

Nitrate 135 

Oxides 135 


Urates 316 

Urea 231 

Uric  acid 316 

Solvents 338 

Urethane 337 

Uropherin 338 

Urotropin 338 

Washing  bottles 362 

Washing  soda lOO 

Water 108 

Experiments  with 406 

Water-bath 366 

Water  of  crystallization. .    18 

Waters no 

Waxes 283 

Weber 23 

Wedge 9 

Weights 

American 26 

Metric 27 

Wheel  and  axle 8 

White  arsenic 177 

White  lead 134 

Wines 262 

Wood's  metal 164 

Wood  spirit 262 

Work 7 

Wulfenite 143 

Xanthin 231,239,316 

Xantho-Creatinine 239 

Yeast 319 

Zinc 124 

Alloys 126 

Amalgams 148 

Compounds 127 

Dental  uses 126 

Experiments 435 

Metallurgy 125 

Reactions 47o 

Solders 126 


586 


INDEX. 


Zinc 

.  Chloride i27 

"        dental  uses  of 128 

Iodide -iSa 

lodo-chloride 132    „  , 

Oxide 129  Zooglcea 


Oxychloride 

Oxyphosphatc... 

Oxysulphate 

Sulphate 

Sulphocarbolate. 


...IS* 
...129 
...131 
...131 
•••335 
,322 


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